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Publication Abstract from PubMed

O-acetylserine sulfhydrylase (OASS) catalyzes the final step of cysteine biosynthesis from O-acetylserine (OAS) and inorganic sulfide in plants and bacteria. Bioinformatics analyses combined with activity assays enabled us to annotate the two putative genes of Microcystis aeruginosa PCC 7806 to CysK1 and CysK2, which encode the two 75% sequence-identical OASS paralogs. Moreover, we solved the crystal structures of CysK1 at 2.30A and cystine-complexed CysK2 at 1.91A, revealing a quite similar overall structure that belongs to the family of fold-type II PLP-dependent enzymes. Structural comparison indicated a significant induced fit upon binding to the cystine, which occupies the binding site for the substrate OAS and blocks the product release tunnel. Subsequent enzymatic assays further confirmed that cystine is a competitive inhibitor of the substrate OAS. Moreover, multiple-sequence alignment revealed that the cystine-binding residues are highly conserved in all OASS proteins, suggesting that this auto-inhibition of cystine might be a universal mechanism of cysteine biosynthesis pathway.

Structural and biochemical analyses of Microcystis aeruginosa O-acetylserine sulfhydrylases reveal a negative feedback regulation of cysteine biosynthesis.,Lu M, Xu BY, Zhou K, Cheng W, Jiang YL, Chen Y, Zhou CZ Biochim Biophys Acta. 2014 Feb;1844(2):308-15. doi: 10.1016/j.bbapap.2013.11.008., Epub 2013 Nov 23. PMID:24275508^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.