Functional analysis of the YidC homologs of Bacillus subtilis: SpoIIIJ and YqjG

PhD ceremony: Mr. M.J. Saller, 13.15 uur, Doopsgezinde Kerk, Oude Boteringestraat 33, Groningen

Dissertation: Functional analysis of the YidC homologs of Bacillus subtilis: SpoIIIJ and YqjG

Promotor(s): prof. A.J.M. Driessen

Faculty: Mathematics and Natural Sciences

The goal of this thesis was the functional characterization of two membrane-integral proteins of Bacillus subtilis, denoted as SpoIIIJ and YqjG. Unlike other members of the YidC/Oxa1/Alb3 protein family, the B. subtilis homologs were proposed to function in protein secretion rather than membrane protein insertion. SpoIIIJ and YgjG were found to functionally complement the growth defect of an E. coli YidC depletion strain and functional analysis showed that SpoIIIJ and YqjG fulfill a role in membrane protein insertion and assembly. Both proteins could be isolated in complex with the entire F1FO ATP synthase, suggests that these proteins fulfill a role in a late stage of the biogenesis of this complex. Using a membrane proteomic study we could confirm that SpoIIIJ fulfills a specific role in sporulation whereas YqjG could be specifically associated with the development of natural competence in Bacillus subtilis that enables the cells to acquire DNA from the environment. In addition, both YidC proteins play a generic role in the assembly of energy transducing complexes and transport proteins showing that the function of the YidC/Oxa1/Alb3 protein family is highly conserved among organisms.