Reviewed, UniProtKB/Swiss-Prot Q43317 (CYSK_CITLA)

Names and origin

Protein names	Recommended name:     Cysteine synthase       Short name=CSase     EC=2.5.1.47 Alternative name(s):     O-acetylserine sulfhydrylase     O-acetylserine (thiol)-lyase       Short name=OAS-TL     Beta-pyrazolylalanine synthase     Beta-PA/CSase     EC=2.5.1.51     L-mimosine synthase     EC=2.5.1.52
Organism	Citrullus lanatus (Watermelon) (Citrullus vulgaris)
Taxonomic identifier	3654 [NCBI]
Taxonomic lineage	Eukaryota › Viridiplantae › Streptophyta › Embryophyta › Tracheophyta › Spermatophyta › Magnoliophyta › eudicotyledons › core eudicotyledons › rosids › eurosids I › Cucurbitales › Cucurbitaceae › Citrullus

Protein attributes

Sequence length	325 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is not processed.
Protein existence	Evidence at transcript level.

General annotation (Comments)

Function	Produces L-cysteine from O-acetyl-L-serine and hydrogen sulfide. Can also use pyrazole and 3,4-dihydroxypyridine instead of the hydrogen sulfide to produce two plant specific non-protein amino acids beta-pyrazolylalanine and L-mimosine. Ref.2 Ref.3
Catalytic activity	O(3)-acetyl-L-serine + H2S = L-cysteine + acetate. O(3)-acetyl-L-serine + pyrazole = 3-(pyrazol-1-yl)-L-alanine + acetate. O(3)-acetyl-L-serine + 3,4-dihydroxypyridine = 3-(3,4-dihydroxypyridin-1-yl)-L-alanine + acetate.
Cofactor	Pyridoxal phosphate.
Pathway	Amino-acid biosynthesis; L-cysteine biosynthesis; L-cysteine from L-serine: step 2/2.
Subunit structure	Homodimer By similarity.
Subcellular location	Cytoplasm By similarity.
Sequence similarities	Belongs to the cysteine synthase/cystathionine beta-synthase family.

Ontologies

Keywords
Biological process	Amino-acid biosynthesis Cysteine biosynthesis
Cellular component	Cytoplasm
Ligand	Pyridoxal phosphate
Molecular function	Transferase
Gene Ontology (GO)
Biological process	cysteine biosynthetic process from serine Inferred from electronic annotation. Source: InterPro
Cellular component	cytoplasm Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular function	L-mimosine synthase activity Inferred from electronic annotation. Source: EC beta-pyrazolylalanine synthase activity Inferred from electronic annotation. Source: EC cysteine synthase activity Inferred from electronic annotation. Source: EC pyridoxal phosphate binding Inferred from electronic annotation. Source: InterPro
Complete GO annotation...

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view	Feature identifier
Molecule processing
	Chain	1 – 325	325	Cysteine synthase		PRO_0000167119
Regions
	Region	184 – 188	5	Pyridoxal phosphate binding By similarity
	Compositional bias	275 – 280	6	Poly-Ala
Sites
	Binding site	80	1	Pyridoxal phosphate By similarity
	Binding site	272	1	Pyridoxal phosphate By similarity
Amino acid modifications
	Modified residue	49	1	N6-(pyridoxal phosphate)lysine By similarity

Sequences

	Sequence		Length	Mass (Da)
	Q43317-1 [UniParc]. Last modified November 1, 1997. Version 1. Checksum: 4A91E6F8AFB5F539	FASTA	325	34,343
	10 20 30 40 50 60 MADAKSTIAK DVTELIGNTP LVYLNRVVDG CVARVAAKLE MMEPCSSVKD RIGYSMISDA 70 80 90 100 110 120 ENKGLITPGE SVLIEPTSGN TGIGLAFIAA AKGYRLIICM PASMSLERRT ILRAFGAELV 130 140 150 160 170 180 LTDPARGMKG AVQKAEEIKA KTPNSYILQQ FENPANPKIH YETTGPEIWR GSGGKIDALV 190 200 210 220 230 240 SGIGTGGTVT GAGKYLKEQN PNIKLYGVEP VESAILSGGK PGPHKIQGIG AGFIPGVLDV 250 260 270 280 290 300 NLLDEVIQVS SEESIETAKL LALKEGLLVG ISSGAAAAAA IRIAKRPENA GKLIVAVFPS 310 320 FGERYLSTVL FESVKRETEN MVFEP

References

[1]	"Molecular cloning of a cysteine synthase cDNA from Citrullus vulgaris (watermelon) by genetic complementation in an Escherichia coli Cys-auxotroph." Noji M., Murakoshi I., Saito K. Mol. Gen. Genet. 244:57-66(1994) [PubMed: 8041362] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA]. Tissue: Seedling.
[2]	"Evidence for identity of beta-pyrazolealanine synthase with cysteine synthase in watermelon: formation of beta-pyrazole-alanine by cloned cysteine synthase in vitro and in vivo." Noji M., Murakoshi I., Saito K. Biochem. Biophys. Res. Commun. 197:1111-1117(1993) [PubMed: 8280125] [Abstract] Cited for: FUNCTION.
[3]	"Production of plant non-protein amino acids by recombinant enzymes of sequential biosynthetic reactions in bacteria." Saito K., Kimura N., Ikegami F., Noji M. Biol. Pharm. Bull. 20:47-53(1997) [PubMed: 9013806] [Abstract] Cited for: FUNCTION.

Cross-references

Sequence databases
EMBLGenBankDDBJ	D28777 mRNA. Translation: BAA05965.1.
PIR	S46438.
3D structure databases
HSSP	HSSP built from PDB template 1OAS based on UniProtKB P12674.
SMR	Q43317. Positions 6-324.
ModBase	Search...
Enzyme and pathway databases
BRENDA	2.5.1.47. 81664. 2.5.1.51. 81664. 2.5.1.52. 81664.
Family and domain databases
InterPro	IPR001216. Cys_synth_BS. IPR005856. Cys_synthKM. IPR005859. CysK. IPR001926. PyrdxlP-dep_enz_bsu. [Graphical view]
Pfam	PF00291. PALP. 1 hit. [Graphical view]
TIGRFAMs	TIGR01139. cysK. 1 hit. TIGR01136. cysKM. 1 hit.
PROSITE	PS00901. CYS_SYNTHASE. 1 hit. [Graphical view]
ProtoNet	Search...

Entry information

Entry name

CYSK_CITLA

Accession

Primary (citable) accession number: Q43317

Entry history

Integrated into UniProtKB/Swiss-Prot:	November 1, 1997
Last sequence update:	November 1, 1997
Last modified:	June 16, 2009
This is version 60 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

PPAP (Plant Proteome Annotation Project)