Structural and phylogenetic analysis of the MotA and MotB families of bacterial flagellar motor proteins

• Published in: Research in microbiology 1996, Vol.147 (5), p.317-332
• Main Authors: Nguyen, C.C., Saier, M.H.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacillus; Bacterial flagellum; Bacterial Proteins - chemistry; Bacterial Proteins - classification; Escherichia coli; Flagelle bactérien; In Vitro Techniques; Molecular Sequence Data; MotA protein; MotB protein; OMP; Phylogeny; Phylogénie; Protéine MotA; Protéine MotB; Rhodobacter sphaeroides
• ISSN: 0923-2508; 1769-7123
• DOI: 10.1016/0923-2508(96)84707-3

MotA and MotB are two well-characterized proteins in Escherichia coli which are believed to function as the proton channel and the anchor, respectively, of the motor component of the bacterial flagellum. We have identified and analysed all currently sequenced members of the MotA and MotB families. Members of these families include (1) these E. coli proteins, (2) their pmf-interacting motor homologues in other bacteria, (3) two ORFs which map downstream of the gene encoding the catabolite repression-mediating CepA protein in Bacillus species and (4) unidentified open reading frames. With one exception (the MotB protein of Rhodobactec sphaeroides), members of the MotB family exhibit a C-terminal domain that is homologous to peptidoglycan-interaction domains of numerous sequenced lipoproteins and outer membrane proteins. Multiple alignments, average hydropathy and similarity plots, and phylogenetic trees have allowed (1) identification of regions of relative conservation, (2) definition of signature sequences for these protein families and (3) determination of relative phylogenetic distances relating all members of each family. The phylogenies of these proteins do not follow those of the organisms from which they were isolated, suggesting the presence of divergent isoforms in many bacteria. Phylogenetic analyses of the peptidoglycan-interaction domains of MotB proteins indicated that, except for MotB of R. sphaeroides, these domains became associated with the MotB proteins early during evolutionary history, before members of the MotB family or members of the outer membrane protein family diverged from each other. MotA et MotB sont deux protéines bien caractérisées chez Escherichia coli dont on pense qu'elles fonctionnent, respectivement, comme un canal pour les protons et une ancre pour le composant moteur du flagelle bactérien. Nous avons identifiéet analysétous les membres des familles MotA et B séquencés actuellement. Les membres de ces familles comprennent (1) les protéines de E. coli citées ci-dessus, (2) leurs homologues moteurs interagissant avec la force motrice des protons chez d'autres bactéries, (3) deux séquences ouvertes de lecture (ORF) situées en aval du gène codant pour la protéine CepA médiatrice de la répression catabolique chez es espèces du genre Bacillus, et (4) des ORFs non identifiées. Avec une exception (la protéine MotB de Rhodobacter sphaeroides), les membres de la famille MotB ont un domaine C-terminal qui est homologue aux domaines