Identification of a novel subunit of respiratory complex I from Thermus thermophilus.

TitleIdentification of a novel subunit of respiratory complex I from Thermus thermophilus.
Publication TypeJournal Article
Year of Publication2006
AuthorsHinchliffe, P, Carroll, J, Sazanov, LA
JournalBiochemistry
Volume45
Issue14
Pagination4413-20
Date Published2006 Apr 11
ISSN0006-2960
KeywordsAmino Acid Sequence, Crystallization, Electron Spin Resonance Spectroscopy, Electron Transport Complex I, Electrophoresis, Polyacrylamide Gel, Molecular Sequence Data, Protein Subunits, Sequence Alignment, Thermus thermophilus
Abstract

The hydrophilic domain (peripheral arm) of the proton-translocating NADH:quinone oxidoreductase (complex I) from the thermophilic organism Thermus thermophilus HB8 has been purified and characterized. The subcomplex is stable in sodium dodecyl sulfate up to 80 degrees C. Of nine iron-sulfur clusters, four to five (one or two binuclear and three tetranuclear) could be detected by EPR in the NADH-reduced enzyme. The preparation consists of eight different polypeptides. Seven of them have been positively identified by peptide mass mapping and N-terminal sequencing as known hydrophilic subunits of T. thermophilus complex I. The eighth polypeptide copurified with the subcomplex at all stages, is strongly associated with the other subunits, and is present in crystals of the subcomplex, used for X-ray data collection. Therefore, it has been identified as a novel complex I subunit and named Nqo15. It is encoded in a locus separate from the nqo operon, containing the 14 other known complex I genes. ORFs encoding Nqo15 homologues are present in the genomes of the closest relatives of T. thermophilus. Our data show that, contrary to previous assumptions, bacterial complex I can contain proteins in addition to a "core" complement of 14 subunits.

DOI10.1021/bi0600998
Alternate JournalBiochemistry
Citation Key10.1021/bi0600998
PubMed ID16584177
Grant ListMC_U105663148 / / Medical Research Council / United Kingdom
MC_U105674180 / / Medical Research Council / United Kingdom