4JTC

Crystal structure of Kv1.2-2.1 paddle chimera channel in complex with Charybdotoxin in Cs+

External Resource: Annotation

Domain Annotation: SCOP/SCOPe Classification
Domain Annotation: SCOP2 Classification
Domain Annotation: ECOD Classification
Domain Annotation: CATH
Protein Family Annotation
Gene Ontology: Gene Product Annotation
InterPro: Protein Family Classification
Membrane Protein Annotation: OPM
Membrane Protein Annotation: PDBTM
Membrane Protein Annotation: MemProtMD
Protein Modification Annotation

Domain Annotation: SCOP/SCOPe Classification SCOP-e Database Homepage

Chains	Domain Info	Class	Fold	Superfamily	Family	Domain	Species	Provenance Source (Version)
A	d4jtca_	Alpha and beta proteins (a/b)	TIM beta/alpha-barrel	NAD(P)-linked oxidoreductase	Aldo-keto reductases (NADP)	Voltage-dependent K+ channel beta subunit	brown rat,rat,rats (Rattus norvegicus ) [TaxId: 10116 ],	SCOPe (2.08)
C [auth G]	d4jtcg_	Alpha and beta proteins (a/b)	TIM beta/alpha-barrel	NAD(P)-linked oxidoreductase	Aldo-keto reductases (NADP)	Voltage-dependent K+ channel beta subunit	brown rat,rat,rats (Rattus norvegicus ) [TaxId: 10116 ],	SCOPe (2.08)
E [auth Y]	d4jtcy_	Small proteins	Knottins (small inhibitors, toxins, lectins)	Scorpion toxin-like	Short-chain scorpion toxins	Charybdotoxin	Yellow scorpion (Leiurus hebraeus ) [TaxId: 2899558 ],	SCOPe (2.08)

Domain Annotation: SCOP2 Classification SCOP2 Database Homepage

Chains	Type	Family Name	Domain Identifier	Family Identifier	Provenance Source (Version)
D [auth H]	SCOP2B Superfamily	POZ domain	8035031	3000894	SCOP2B (2022-06-29)
B	SCOP2B Superfamily	POZ domain	8035031	3000894	SCOP2B (2022-06-29)
A	SCOP2B Superfamily	NAD(P)-linked oxidoreductase	8040991	3000288	SCOP2B (2022-06-29)
C [auth G]	SCOP2B Superfamily	NAD(P)-linked oxidoreductase	8040991	3000288	SCOP2B (2022-06-29)
E [auth Y]	SCOP2B Superfamily	Scorpion toxin-like	8038204	3000309	SCOP2B (2022-06-29)

Domain Annotation: ECOD Classification ECOD Database Homepage

Chains	Family Name	Domain Identifier	Architecture	Possible Homology	Homology	Topology	Family	Provenance Source (Version)
D [auth H]	Ion_trans	e4jtcH1	A: alpha complex topology	X: Voltage-gated ion channels (From Topology)	H: Voltage-gated ion channels (From Topology)	T: Voltage-gated ion channels	F: Ion_trans	ECOD (1.6)
D [auth H]	BTB_2	e4jtcH2	A: a+b two layers	X: POZ domain (From Topology)	H: POZ domain (From Topology)	T: POZ domain	F: BTB_2	ECOD (1.6)
B	Ion_trans	e4jtcB2	A: alpha complex topology	X: Voltage-gated ion channels (From Topology)	H: Voltage-gated ion channels (From Topology)	T: Voltage-gated ion channels	F: Ion_trans	ECOD (1.6)
B	BTB_2	e4jtcB3	A: a+b two layers	X: POZ domain (From Topology)	H: POZ domain (From Topology)	T: POZ domain	F: BTB_2	ECOD (1.6)
A	Aldo_ket_red	e4jtcA1	A: a/b barrels	X: TIM beta/alpha-barrel	H: TIM barrels (From Topology)	T: TIM barrels	F: Aldo_ket_red	ECOD (1.6)
C [auth G]	Aldo_ket_red	e4jtcG1	A: a/b barrels	X: TIM beta/alpha-barrel	H: TIM barrels (From Topology)	T: TIM barrels	F: Aldo_ket_red	ECOD (1.6)
E [auth Y]	Toxin_2	e4jtcY1	A: few secondary structure elements	X: omega toxin-like	H: omega toxin-related	T: Scorpion toxin-like	F: Toxin_2	ECOD (1.6)

Domain Annotation: CATH CATH Database Homepage

Chain	Domain	Class	Architecture	Topology	Homology	Provenance Source (Version)
D [auth H]	3.30.710.10	Alpha Beta	2-Layer Sandwich	Potassium Channel Kv1.1	Chain A	CATH (4.3.0)
D [auth H]	1.20.120.350	Mainly Alpha	Up-down Bundle	Four Helix Bundle (Hemerythrin (Met), subunit A)	Voltage-gated potassium channels. Chain C	CATH (4.3.0)
D [auth H]	1.10.287.70	Mainly Alpha	Orthogonal Bundle	Helix Hairpins		CATH (4.3.0)
B	3.30.710.10	Alpha Beta	2-Layer Sandwich	Potassium Channel Kv1.1	Chain A	CATH (4.3.0)
B	1.20.120.350	Mainly Alpha	Up-down Bundle	Four Helix Bundle (Hemerythrin (Met), subunit A)	Voltage-gated potassium channels. Chain C	CATH (4.3.0)
B	1.10.287.70	Mainly Alpha	Orthogonal Bundle	Helix Hairpins		CATH (4.3.0)
A	3.20.20.100	Alpha Beta	Alpha-Beta Barrel	TIM Barrel	NADP-dependent oxidoreductase domain	CATH (4.3.0)
C [auth G]	3.20.20.100	Alpha Beta	Alpha-Beta Barrel	TIM Barrel	NADP-dependent oxidoreductase domain	CATH (4.3.0)

Protein Family Annotation Pfam Database Homepage

Chains	Accession	Name	Description	Comments	Source
B, D [auth H]	PF07885	Ion channel (Ion_trans_2)	Ion channel	-	Family
B, D [auth H]	PF02214	BTB/POZ domain (BTB_2)	BTB/POZ domain	In voltage-gated K+ channels this domain is responsible for subfamily-specific assembly of alpha-subunits into functional tetrameric channels [1]. In KCTD1 (Swiss:Q719H9) this domain functions as a transcriptional repressor [2]. It also mediates homo ...	In voltage-gated K+ channels this domain is responsible for subfamily-specific assembly of alpha-subunits into functional tetrameric channels [1]. In KCTD1 (Swiss:Q719H9) this domain functions as a transcriptional repressor [2]. It also mediates homomultimerisation of KCTD1 and interaction of KCTD1 with the transcription factor AP-2-alpha [2-3].	Domain
B, D [auth H]	PF00520	Ion transport protein (Ion_trans)	Ion transport protein	-	Family
A, C [auth G]	PF00248	Aldo/keto reductase family (Aldo_ket_red)	Aldo/keto reductase family	This family includes a number of K+ ion channel beta chain regulatory domains - these are reported to have oxidoreductase activity [2].	Domain
E [auth Y]	PF00451	Scorpion short toxin, BmKK2 (Toxin_2)	Scorpion short toxin, BmKK2	Members of this family, which are found in various scorpion toxins, confer potassium channel blocking activity [1].	Domain

Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage

Chains	Polymer	Molecular Function	Biological Process	Cellular Component
B, D [auth H]	Potassium voltage-gated channel subfamily A member 2, Potassium voltage-gated channel subfamily B member 1	monoatomic cation transmembrane transporter activity gated channel activity monoatomic ion channel activity potassium ion transmembrane transporter activity voltage-gated channel activity voltage-gated monoatomic ion channel activity potassium channel activity voltage-gated monoatomic cation channel activity monoatomic cation channel activity passive transmembrane transporter activity voltage-gated potassium channel activity inorganic molecular entity transmembrane transporter activity channel activity inorganic cation transmembrane transporter activity monoatomic ion transmembrane transporter activity monoatomic cation transmembrane transporter activity gated channel activity monoatomic ion channel activity potassium ion transmembrane transporter activity voltage-gated channel activity voltage-gated monoatomic ion channel activity potassium channel activity voltage-gated monoatomic cation channel activity monoatomic cation channel activity passive transmembrane transporter activity voltage-gated potassium channel activity inorganic molecular entity transmembrane transporter activity channel activity inorganic cation transmembrane transporter activity monoatomic ion transmembrane transporter activity transporter activity metal ion transmembrane transporter activity transmembrane transporter activity delayed rectifier potassium channel activity protein heterodimerization activity protein binding binding protein dimerization activity transmembrane transporter binding SNARE binding outward rectifier potassium channel activity cytoskeletal protein binding kinesin binding voltage-gated monoatomic ion channel activity involved in regulation of postsynaptic membrane potential voltage-gated monoatomic ion channel activity involved in regulation of presynaptic membrane potential	response to stimulus response to stress response to wounding response to axon injury transport monoatomic ion transmembrane transport potassium ion transmembrane transport inorganic ion transmembrane transport establishment of localization metal ion transport inorganic cation transmembrane transport transmembrane transport monoatomic cation transmembrane transport localization response to stimulus response to stress response to wounding response to axon injury transport monoatomic ion transmembrane transport potassium ion transmembrane transport inorganic ion transmembrane transport establishment of localization metal ion transport inorganic cation transmembrane transport transmembrane transport monoatomic cation transmembrane transport localization monoatomic ion transport potassium ion transport cellular process monoatomic cation transport cellular response to stimulus cellular response to nutrient levels response to nutrient levels protein localization protein localization to cell periphery cellular localization protein localization to plasma membrane cellular macromolecule localization macromolecule localization localization within membrane protein localization to membrane regulation of biological process regulation of cellular process cell surface receptor signaling pathway signaling biological regulation glutamate receptor signaling pathway cell communication signal transduction cellular response to metal ion cellular response to chemical stimulus response to metal ion response to chemical cellular response to calcium ion response to calcium ion monoamine transport regulation of localization nitrogen compound transport regulation of catecholamine secretion positive regulation of biological process organic hydroxy compound transport positive regulation of secretion by cell positive regulation of amine transport secretion by cell regulation of secretion by cell catecholamine transport positive regulation of secretion positive regulation of cellular process secretion regulation of transport positive regulation of catecholamine secretion export from cell regulation of secretion catecholamine secretion amine transport positive regulation of transport regulation of amine transport regulated exocytosis regulation of calcium ion-dependent exocytosis vesicle-mediated transport positive regulation of exocytosis regulation of regulated secretory pathway positive regulation of regulated secretory pathway calcium-ion regulated exocytosis positive regulation of calcium ion-dependent exocytosis regulation of vesicle-mediated transport exocytosis regulation of exocytosis response to acid chemical response to oxygen-containing compound response to nitrogen compound response to L-glutamate response to amino acid modulation of chemical synaptic transmission negative regulation of signaling negative regulation of biological process negative regulation of synaptic transmission negative regulation of cell communication synaptic signaling positive regulation of long-term synaptic depression negative regulation of cellular process regulation of biological quality regulation of synaptic plasticity trans-synaptic signaling regulation of signaling cell-cell signaling chemical synaptic transmission regulation of trans-synaptic signaling anterograde trans-synaptic signaling long-term synaptic depression regulation of long-term synaptic depression regulation of cell communication chemical homeostasis homeostatic process glucose homeostasis carbohydrate homeostasis establishment of protein localization regulation of protein localization protein targeting positive regulation of establishment of protein localization regulation of protein targeting to membrane regulation of protein localization to membrane establishment of protein localization to membrane regulation of establishment of protein localization positive regulation of protein localization to membrane protein targeting to membrane regulation of cellular localization regulation of protein targeting positive regulation of protein localization positive regulation of protein targeting to membrane neuron apoptotic process regulation of apoptotic process regulation of programmed cell death regulation of motor neuron apoptotic process motor neuron apoptotic process cell death apoptotic process programmed cell death regulation of neuron apoptotic process action potential regulation of membrane potential cellular response to glucose stimulus intracellular glucose homeostasis cellular response to oxygen-containing compound response to hexose cellular response to carbohydrate stimulus cellular homeostasis response to monosaccharide response to carbohydrate response to glucose cellular response to hexose stimulus intracellular chemical homeostasis cellular response to monosaccharide stimulus multicellular organismal process cellular developmental process cell development cellular component organization neurogenesis multicellular organism development neuron differentiation cell differentiation anatomical structure development cellular component organization or biogenesis cell maturation system development membrane organization developmental process developmental maturation nervous system development neuronal ion channel clustering generation of neurons clustering of voltage-gated potassium channels anatomical structure maturation neuron development neuron maturation membrane docking organelle localization by membrane tethering organelle localization vesicle docking exocytic process vesicle docking involved in exocytosis regulation of action potential export across plasma membrane potassium ion export across plasma membrane negative regulation of protein transport negative regulation of transport negative regulation of secretion negative regulation of hormone secretion negative regulation of secretion by cell regulation of peptide hormone secretion negative regulation of peptide hormone secretion regulation of hormone levels establishment of protein localization to extracellular region negative regulation of establishment of protein localization protein secretion regulation of protein secretion negative regulation of protein secretion regulation of hormone secretion regulation of peptide secretion hormone secretion protein localization to extracellular region negative regulation of peptide secretion peptide secretion amide transport signal release negative regulation of protein localization regulation of peptide transport regulation of protein transport peptide transport negative regulation of insulin secretion protein transport regulation of insulin secretion peptide hormone secretion hormone transport insulin secretion cellular component biogenesis cellular component assembly protein-containing complex organization protein complex oligomerization protein-containing complex assembly protein homooligomerization norepinephrine transport positive regulation of norepinephrine secretion organic cation transport norepinephrine secretion regulation of norepinephrine secretion corpus callosum development head development forebrain development animal organ development brain development central nervous system development telencephalon development nerve development cranial nerve development optic nerve development dopamine transport dopamine secretion regulation of dopamine secretion cranial nerve morphogenesis anatomical structure morphogenesis cranial nerve structural organization anatomical structure arrangement optic nerve morphogenesis optic nerve structural organization system process nervous system process transmission of nerve impulse neuronal action potential circadian sleep/wake cycle, sleep rhythmic process circadian sleep/wake cycle rhythmic behavior circadian rhythm regulation of circadian sleep/wake cycle regulation of circadian sleep/wake cycle, non-REM sleep regulation of circadian rhythm circadian sleep/wake cycle, non-REM sleep behavior regulation of behavior circadian behavior sleep regulation of multicellular organismal process regulation of circadian sleep/wake cycle, sleep circadian sleep/wake cycle process pallium development cerebral cortex development sensory perception sensory perception of pain	cell periphery postsynapse postsynaptic membrane synapse cell junction membrane plasma membrane plasma membrane region cellular anatomical entity synaptic membrane somatodendritic compartment cell body perikaryon neuronal cell body cell periphery postsynapse postsynaptic membrane synapse cell junction membrane plasma membrane plasma membrane region cellular anatomical entity synaptic membrane somatodendritic compartment cell body perikaryon neuronal cell body cell projection proximal dendrite dendrite dendritic tree neuron projection plasma membrane bounded cell projection sarcolemma cholinergic synapse intracellular anatomical structure perinuclear region of cytoplasm cytoplasm neuronal cell body membrane cell body membrane axon apical part of cell apical plasma membrane cell surface postsynaptic specialization membrane postsynaptic specialization organelle voltage-gated potassium channel complex protein-containing complex plasma membrane protein complex potassium channel complex membrane protein complex cation channel complex transporter complex transmembrane transporter complex monoatomic ion channel complex cell leading edge leading edge membrane neuron projection membrane dendrite membrane cell projection membrane lateral plasma membrane lamellipodium main axon juxtaparanode region of axon cell-cell junction anchoring junction paranodal junction presynapse presynaptic membrane axon initial segment glutamatergic synapse membrane-bounded organelle organelle subcompartment intracellular membrane-bounded organelle endomembrane system endoplasmic reticulum subcompartment intracellular organelle nuclear outer membrane-endoplasmic reticulum membrane network endoplasmic reticulum organelle membrane endoplasmic reticulum membrane lamellipodium membrane axon terminus distal axon calyx of Held neuron projection terminus endosome intracellular vesicle cytoplasmic vesicle vesicle
A, C [auth G]	Voltage-gated potassium channel subunit beta-2	methylglyoxal reductase (NADPH) (acetol producing) activity oxidoreductase activity oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor oxidoreductase activity, acting on CH-OH group of donors catalytic activity monoatomic cation transmembrane transporter activity gated channel activity monoatomic ion channel activity potassium ion transmembrane transporter activity voltage-gated channel activity voltage-gated monoatomic ion channel activity potassium channel activity voltage-gated monoatomic cation channel activity monoatomic cation channel activity methylglyoxal reductase (NADPH) (acetol producing) activity oxidoreductase activity oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor oxidoreductase activity, acting on CH-OH group of donors catalytic activity monoatomic cation transmembrane transporter activity gated channel activity monoatomic ion channel activity potassium ion transmembrane transporter activity voltage-gated channel activity voltage-gated monoatomic ion channel activity potassium channel activity voltage-gated monoatomic cation channel activity monoatomic cation channel activity passive transmembrane transporter activity voltage-gated potassium channel activity inorganic molecular entity transmembrane transporter activity channel activity inorganic cation transmembrane transporter activity monoatomic ion transmembrane transporter activity transporter activity metal ion transmembrane transporter activity transmembrane transporter activity protein binding binding transmembrane transporter binding aldo-keto reductase (NADPH) activity alcohol dehydrogenase [NAD(P)+] activity protein-containing complex binding potassium channel regulator activity channel regulator activity ion channel regulator activity molecular function regulator activity transporter regulator activity	developmental process muscle structure development cellular developmental process cell differentiation anatomical structure development cellular process myoblast differentiation protein localization regulation of localization cellular localization regulation of biological process regulation of cellular process regulation of protein localization biological regulation developmental process muscle structure development cellular developmental process cell differentiation anatomical structure development cellular process myoblast differentiation protein localization regulation of localization cellular localization regulation of biological process regulation of cellular process regulation of protein localization biological regulation localization protein localization to cell surface regulation of cellular localization cellular macromolecule localization macromolecule localization regulation of protein localization to cell surface regulation of action potential action potential regulation of biological quality regulation of membrane potential nucleoside phosphate metabolic process nicotinamide nucleotide metabolic process cellular metabolic process primary metabolic process nucleotide metabolic process purine-containing compound metabolic process NADP metabolic process nucleobase-containing compound metabolic process purine nucleotide metabolic process organophosphate metabolic process nucleobase-containing small molecule metabolic process phosphate-containing compound metabolic process pyridine-containing compound metabolic process metabolic process small molecule metabolic process NADPH oxidation phosphorus metabolic process pyridine nucleotide metabolic process multicellular organismal process system process nervous system process neuromuscular process regulation of potassium ion transport transport monoatomic ion transmembrane transport potassium ion transmembrane transport regulation of monoatomic ion transmembrane transport metal ion transport monoatomic cation transmembrane transport monoatomic ion transport monoatomic cation transport regulation of metal ion transport regulation of transport regulation of monoatomic ion transport inorganic ion transmembrane transport regulation of potassium ion transmembrane transport establishment of localization inorganic cation transmembrane transport transmembrane transport regulation of transmembrane transport potassium ion transport regulation of monoatomic cation transmembrane transport hemopoiesis cell development hematopoietic progenitor cell differentiation	postsynaptic specialization membrane postsynaptic specialization synapse membrane plasma membrane cellular anatomical entity postsynaptic density membrane synaptic membrane cell periphery postsynaptic density postsynapse neuron to neuron synapse organelle cell junction postsynaptic specialization membrane postsynaptic specialization synapse membrane plasma membrane cellular anatomical entity postsynaptic density membrane synaptic membrane cell periphery postsynaptic density postsynapse neuron to neuron synapse organelle cell junction postsynaptic membrane asymmetric synapse plasma membrane region axon cell projection main axon juxtaparanode region of axon neuron projection plasma membrane bounded cell projection intracellular anatomical structure cytoplasm cytosol axon initial segment glutamatergic synapse voltage-gated potassium channel complex protein-containing complex plasma membrane protein complex potassium channel complex membrane protein complex cation channel complex transporter complex transmembrane transporter complex monoatomic ion channel complex intracellular organelle cytoskeleton intracellular non-membrane-bounded organelle non-membrane-bounded organelle pinceau fiber axon terminus presynapse distal axon neuron projection terminus cytoplasmic side of plasma membrane cytoplasmic side of membrane side of membrane
E [auth Y]	Potassium channel toxin alpha-KTx 1.1	molecular function inhibitor activity channel regulator activity transporter inhibitor activity ion channel inhibitor activity ion channel regulator activity molecular function regulator activity transporter regulator activity channel inhibitor activity potassium channel regulator activity toxin activity	biological process involved in interspecies interaction between organisms response to stimulus response to other organism defense response response to external stimulus response to biotic stimulus defense response to bacterium defense response to other organism response to stress response to bacterium response to external biotic stimulus defense response to fungus response to fungus cellular process biological process involved in interspecies interaction between organisms response to stimulus response to other organism defense response response to external stimulus response to biotic stimulus defense response to bacterium defense response to other organism response to stress response to bacterium response to external biotic stimulus defense response to fungus response to fungus cellular process disruption of cell in another organism disruption of anatomical structure in another organism killing of cells of another organism cell killing	extracellular region cellular anatomical entity

InterPro: Protein Family Classification InterPro Database Homepage

Chains	Accession	Name	Type
B, D [auth H]	IPR003973	Potassium channel, voltage dependent, Kv2	Family
B, D [auth H]	IPR003968	Potassium channel, voltage dependent, Kv	Family
B, D [auth H]	IPR004350	Potassium channel, voltage dependent, Kv2.1	Family
B, D [auth H]	IPR003131	Potassium channel tetramerisation-type BTB domain	Domain
B, D [auth H]	IPR011333	SKP1/BTB/POZ domain superfamily	Homologous Superfamily
B, D [auth H]	IPR000210	BTB/POZ domain	Domain
B, D [auth H]	IPR005821	Ion transport domain	Domain
B, D [auth H]	IPR027359	Voltage-dependent channel domain superfamily	Homologous Superfamily
B, D [auth H]	IPR003972	Potassium channel, voltage dependent, Kv1	Family
B, D [auth H]	IPR000210	BTB/POZ domain	Domain
B, D [auth H]	IPR003968	Potassium channel, voltage dependent, Kv	Family
B, D [auth H]	IPR005821	Ion transport domain	Domain
B, D [auth H]	IPR003131	Potassium channel tetramerisation-type BTB domain	Domain
B, D [auth H]	IPR004049	Potassium channel, voltage dependent, Kv1.2	Family
B, D [auth H]	IPR011333	SKP1/BTB/POZ domain superfamily	Homologous Superfamily
B, D [auth H]	IPR027359	Voltage-dependent channel domain superfamily	Homologous Superfamily
A, C [auth G]	IPR005399	Potassium channel, voltage-dependent, beta subunit, KCNAB-related	Family
A, C [auth G]	IPR036812	NADP-dependent oxidoreductase domain superfamily	Homologous Superfamily
A, C [auth G]	IPR005401	Potassium channel, voltage-dependent, beta subunit, KCNAB2	Family
A, C [auth G]	IPR023210	NADP-dependent oxidoreductase domain	Domain
A, C [auth G]	IPR005983	Potassium channel, voltage-dependent, beta subunit, KCNAB	Family
E [auth Y]	IPR036574	Knottin, scorpion toxin-like superfamily	Homologous Superfamily
E [auth Y]	IPR001947	Scorpion short chain toxin, potassium channel inhibitor	Family

Membrane Protein Annotation: OPM OPM Database Homepage

Chains	External Link	Type	Class	Superfamily	Family
A, B, C [auth G], D [auth H], E [auth Y]	OPM	Transmembrane	Alpha-helical polytopic	Ion channel (VIC) superfamily	KvAP voltage-regulated K channels

Membrane Protein Annotation: PDBTM PDBTM Database Homepage

Chains	External Link	Comment
A, B, C [auth G], D [auth H], E [auth Y]	PDBTM	Annotated as membrane protein by PDBTM

Membrane Protein Annotation: MemProtMD MemProtMD Database Homepage

Chains	External Link	Comment
A, B, C [auth G], D [auth H], E [auth Y]	MemProtMD	Annotated as membrane protein by MemProtMD

Protein Modification Annotation

Modified Residue(s)
Chain	Residue(s)	Description
E [auth Y]	PCA	Parent Component: GLN RESID: AA0031 PSI-MOD : 2-pyrrolidone-5-carboxylic acid (Gln) MOD:00040 , 2-pyrrolidone-5-carboxylic acid (Glu) MOD:00420