3a9z | pdb_00003a9z
Crystal structure of ras selenocysteine lyase in complex with selenopropionate
Structural highlights
Function[SCLY_RAT] Catalyzes the decomposition of L-selenocysteine to L-alanine and elemental selenium (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSelenocysteine lyase (SCL) catalyzes the pyridoxal 5'-phosphate-dependent removal of selenium from l-selenocysteine to yield l-alanine. The enzyme is proposed to function in the recycling of the micronutrient selenium from degraded selenoproteins containing selenocysteine residue as an essential component. The enzyme exhibits strict substrate specificity toward l-selenocysteine and no activity to its cognate l-cysteine. However, it remains unclear how the enzyme distinguishes between selenocysteine and cysteine. Here, we present mechanistic studies of selenocysteine lyase from rat. ESI-MS analysis of wild-type and C375A mutant SCL revealed that the catalytic reaction proceeds via the formation of an enzyme-bound selenopersulfide intermediate on the catalytically essential Cys-375 residue. UV-visible spectrum analysis and the crystal structure of SCL complexed with l-cysteine demonstrated that the enzyme reversibly forms a nonproductive adduct with l-cysteine. Cys-375 on the flexible loop directed l-selenocysteine, but not l-cysteine, to the correct position and orientation in the active site to initiate the catalytic reaction. These findings provide, for the first time, the basis for understanding how trace amounts of a selenium-containing substrate is distinguished from excessive amounts of its cognate sulfur-containing compound in a biological system. Reaction mechanism and molecular basis for selenium/sulfur discrimination of selenocysteine lyase.,Omi R, Kurokawa S, Mihara H, Hayashi H, Goto M, Miyahara I, Kurihara T, Hirotsu K, Esaki N J Biol Chem. 2010 Apr 16;285(16):12133-9. Epub 2010 Feb 17. PMID:20164179[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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