Recent studies have shown that there is a pathway that is evolutionarily conserved for insertion of proteins into membrane in mitochondria, chloroplasts, and bacteria. In this pathway, Oxa1/Alb3/YidC proteins are believed to function as membrane insertases that play an important role in the process of membrane protein biogenesis. Additional tasks of the Oxa1/Alb3/YidC members may be in integrating membrane proteins into the lipid bilayer, as well as in folding and assemblying proteins into membrane protein complexes. The objective of this research is to investigate the functions of YidC in Escherichia coli and other critical components including the Sec translocase, SRP and energetics for membrane protein biogenesis. In particular, the membrane complexes playing central roles in respiratory and energy transduction, such as the subunits of the F0 sector of the F1F0ATP synthase, have been studied. YidC was discovered to play a critical role for insertion of the Sec-independent M13 procoat and Pf3 coat phage proteins. YidC is also essential for Escherichia coli viability. To determine whether there is an absolute requirement of YidC for membrane protein insertion of any endogenous proteins, we investigated a few representative membrane proteins. We found that membrane subunits of the F0 sector of F1F0ATP synthase and SecE protein of SecYEG translocase are highly dependent on YidC for membrane insertion. These studies establish that physiological substrates of YidC include subunits of ATP synthase and SecYEG translocase. We continue to investigate membrane protein biogenesis of F0 sector subunits of F1F0ATP synthase. We show that Sec translocase and SRP pathway are required for membrane insertion of subunit a and b. In contrast, subunit c required neither Sec machinery nor SRP pathway for insertion. While proton motive force (pmf) was not required for insertion of subunit b and c, it was required for translocation of negatively charged periplasmic N-terminal tail of subunit a, whereas periplasmic loop 2 of subunit a could insert in a pmf-independent manner. Taken together, the in vivo data show that subunit a and b are inserted by Sec/SRP pathway with help of YidC, and subunit c is integrated into membrane by the novel YidC pathway.
|School:||The Ohio State University|
|Department:||Molecular, Cellular, and Developmental Biology|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Keywords:||E. coli, Insertion, Membrane, Membrane protein insertion, Protein, Yidc|
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