title: Characterization of a monothiol glutaredoxin encoded by Chlorella virus PBCV-1.
abstract: Annotation of the 330-kb Chlorella virus PBCV-1 genome identified a 237 nucleotide gene (a438l) that codes for a protein with approximately 35% amino acid identity to glutaredoxins (Grx) found in other organisms. The PBCV-1 protein resembles classical Grxs in both size (9 kDa) and location of the active site (N-terminus). However, the PBCV-1 Grx is unusual because it contains a monothiol active site (CPYS) rather than the typical dithiol active site (CPYC). To examine this unique active site, four site-specific mutants (CPYC, CPYA, SPYC, and SPYS) were constructed to determine if the N-terminal cysteine is necessary for enzyme activity. Wild type and both mutants containing N-terminal cysteines catalyzed the reduction of disulfides in a coupled system with GSH, NADPH, and glutathione reductase. However, both mutants with an altered N-terminal cysteine were inactive. The grx gene is common in the Chlorella viruses. Molecular phylogenetic analyses of the PBCV-1 enzyme support its relatedness to those from other Chlorella viruses and yet demonstrate the divergence of the Grx molecule.
authors.affiliation: Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583, USA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Fitzgerald
authors.forename: Yuanzheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Gentry
authors.initials: G
authors.lastname: Lewis
authors.forename: James L
authors.initials: JL
authors.lastname: Van Etten
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002708:Chlorella / Q000821:virology*; D054477:Glutaredoxins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D017862:Phycodnaviridae / Q000201:enzymology* / Q000235:genetics*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D054477:Glutaredoxins; D014764:Viral Proteins
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