title: Evolution of the soluble nitrate reductase: defining the monomeric periplasmic nitrate reductase subgroup.
abstract: Bacterial nitrate reductases can be classified into at least three groups according to their localization and function, namely membrane-bound (NAR) or periplasmic (NAP) respiratory and cytoplasmic assimilatory (NAS) enzymes. Monomeric NASs are the simplest of the soluble nitrate reductases, although heterodimeric NASs exist, and a common structural arrangement of NAP is that of a NapAB heterodimer. Using bioinformatic analysis of published genomes, we have identified more representatives of a monomeric class of NAP, which is the evolutionary link between the monomeric NASs and the heterodimeric NAPs. This has further established the monomeric structural clade of NAP. The operons of the monomeric NAP do not contain NapB and suggest that other redox partners are employed by these enzymes, including NapM or NapG predicted proteins. A structural alignment and comparison of the monomeric and heterodimeric NAPs suggests that a difference in surface polarity is related to the interaction of the respective catalytic subunit and redox partner.
authors.affiliation: Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK. b.jepson@uea.ac.uk
authors.forename: B J N
authors.initials: BJ
authors.lastname: Jepson
authors.forename: A
authors.initials: A
authors.lastname: Marietou
authors.forename: S
authors.initials: S
authors.lastname: Mohan
authors.forename: J A
authors.initials: JA
authors.lastname: Cole
authors.forename: C S
authors.initials: CS
authors.lastname: Butler
authors.forename: D J
authors.initials: DJ
authors.lastname: Richardson
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D008958:Models, Molecular; D005810:Multigene Family; D009565:Nitrate Reductases / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny
chemical_list: D001426:Bacterial Proteins; D009565:Nitrate Reductases