Characterization of a monothiol glutaredoxin encoded by Chlorella virus PBCV-1

Authors

Lisa A. Fitzgerald, University of Nebraska-LincolnFollow
Yuanzheng Zhang, University of Nebraska-Lincoln
Gentry L. Lewis, University of Nebraska-LincolnFollow
James L. Van Etten, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2009

Comments

Published in Virus Genes, August 2009. Copyright Springer Science+Business Media, LLC 2009. Used by permission

Abstract

Annotation of the 330-kb Chlorella virus PBCV-1 genome identified a 237 nucleotide gene (a438l) that codes for a protein with ~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 sitespecific 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.