Journal article
Covalent Flavinylation of Monomeric Sarcosine Oxidase: Identification of a Residue Essential for Holoenzyme Biosynthesis
Biochemistry (Easton), Vol.47(4), pp.1136-1143
01 Jan 2008
Abstract
FAD in monomeric sarcosine oxidase (MSOX) is covalently linked to the protein by a thioether linkage between its 8alpha-methyl group and Cys315. Covalent flavinylation of apoMSOX has been shown to proceed via an autocatalytic reaction that requires only FAD and is blocked by a mutation of Cys315. His45 and Arg49 are located just above the si-face of the flavin ring, near the site of covalent attachment. His45Ala and His45Asn mutants contain covalently bound FAD and exhibit catalytic properties similar to wild-type MSOX. The results rule out a significant role for His45 in covalent flavinylation or sarcosine oxidation. In contrast, Arg49Ala and Arg49Gln mutants are isolated as catalytically inactive apoproteins. ApoArg49Ala forms a stable noncovalent complex with reduced 5-deazaFAD that exhibits properties similar to those observed for the corresponding complex with apoCys315Ala. The results show that elimination of a basic residue at position 49 blocks covalent flavinylation but does not prevent noncovalent flavin binding. The Arg49Lys mutant contains covalently bound FAD, but its flavin content is similar to 4- fold lower than wild-type MSOX. However, most of the apoprotein in the Arg49Lys preparation is reconstitutable with FAD in a reaction that exhibits kinetic parameters similar to those observed for flavinylation of wild-type apoMSOX. Although covalent flavinylation is scarcely affected, the specific activity of the Arg49Lys mutant is only 4% of that observed with wild-type MSOX. The results show that a basic residue at position 49 is essential for covalent flavinylation of MSOX and suggest that Arg49 also plays an important role in sarcosine oxidation.
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Details
- Title
- Covalent Flavinylation of Monomeric Sarcosine Oxidase: Identification of a Residue Essential for Holoenzyme Biosynthesis
- Creators
- Alshaimaa Hassan-AbdallahGuohua ZhaoMarilyn Schuman Jorns
- Publication Details
- Biochemistry (Easton), Vol.47(4), pp.1136-1143
- Publisher
- American Chemical Society; Washington, DC
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Biochemistry and Molecular Biology
- Identifiers
- 991014877818804721