RESUMO
Eight different Bacillus subtilis strains and Bacillus atrophaeus were found to produce the bacteriocin subtilosin A. On the basis of the subtilosin gene (sbo) sequences two distinct classes of B. subtilis strains were distinguished, and they fell into the two B. subtilis subspecies (B. subtilis subsp. subtilis and B. subtilis subsp. spizizenii). The entire sequence of the subtilosin gene cluster of a B. subtilis subsp. spizizenii strain, B. subtilis ATCC 6633, was determined. This sequence exhibited a high level of homology to the sequence of the sbo-alb gene locus of B. subtilis 168. By using primer extension analysis the transcriptional start sites of sbo in B. subtilis strains ATCC 6633 and 168 were found to be 47 and 45 bp upstream of the sbo start codon, respectively. Our results provide insight into the incipient evolutionary divergence of the two B. subtilis subspecies.
Assuntos
Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Genes Bacterianos , Família Multigênica , Peptídeos/genética , Alelos , Sequência de Aminoácidos , Bacteriocinas , Sequência de Bases , DNA Bacteriano/genética , Evolução Molecular , Variação Genética , Dados de Sequência Molecular , Peptídeos Cíclicos , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Especificidade da EspécieRESUMO
Stable supercomplexes of bacterial respiratory chain complexes III (ubiquinol:cytochrome c oxidoreductase) and IV (cytochrome c oxidase) have been isolated as early as 1985 (Berry, E. A., and Trumpower, B. L. (1985) J. Biol. Chem. 260, 2458-2467). However, these assemblies did not comprise complex I (NADH:ubiquinone oxidoreductase). Using the mild detergent digitonin for solubilization of Paracoccus denitrificans membranes we could isolate NADH oxidase, assembled from complexes I, III, and IV in a 1:4:4 stoichiometry. This is the first chromatographic isolation of a complete "respirasome." Inactivation of the gene for tightly bound cytochrome c552 did not prevent formation of this supercomplex, indicating that this electron carrier protein is not essential for structurally linking complexes III and IV. Complex I activity was also found in the membranes of mutant strains lacking complexes III or IV. However, no assembled complex I but only dissociated subunits were observed following the same protocols used for electrophoretic separation or chromatographic isolation of the supercomplex from the wild-type strain. This indicates that the P. denitrificans complex I is stabilized by assembly into the NADH oxidase supercomplex. In addition to substrate channeling, structural stabilization of a membrane protein complex thus appears as one of the major functions of respiratory chain supercomplexes.
