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Publication Abstract from PubMed

The unique monooxygenase activity of cytochrome P450cam has been attributed to coordination of a cysteine thiolate to the heme cofactor. To investigate this interaction, we replaced cysteine with the more electron-donating selenocysteine. Good yields of the selenoenzyme were obtained by bacterial expression of an engineered gene containing the requisite UGA codon for selenocysteine and a simplified yet functional selenocysteine insertion sequence (SECIS). The sulfur-to-selenium substitution subtly modulates the structural, electronic, and catalytic properties of the enzyme. Catalytic activity decreases only 2-fold, whereas substrate oxidation becomes partially uncoupled from electron transfer, implying a more complex role for the axial ligand than generally assumed.

Probing the role of the proximal heme ligand in cytochrome P450cam by recombinant incorporation of selenocysteine.,Aldag C, Gromov IA, Garcia-Rubio I, von Koenig K, Schlichting I, Jaun B, Hilvert D Proc Natl Acad Sci U S A. 2009 Mar 17. PMID:19293375^[1]

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