Mitochondrial-bacterial hybrids of BamA/Tob55 suggest variable requirements for the membrane integration of beta-barrel proteins

作者：Pfitzner Anna Katharina; Steblau Nadja; Ulrich Thomas; Oberhettinger Philipp; Autenrieth Ingo B; Schuetz Monika; Rapaport Doron^*

来源：Scientific Reports, 2016, 6(1): 39053.

DOI：10.1038/srep39053

beta-Barrel proteins are found in the outer membrane (OM) of Gram-negative bacteria, chloroplasts and mitochondria. The assembly of these proteins into the corresponding OM is facilitated by a dedicated protein complex that contains a central conserved beta-barrel protein termed BamA in bacteria and Tob55/Sam50 in mitochondria. BamA and Tob55 consist of a membrane-integral C-terminal domain that forms a beta-barrel pore and a soluble N-terminal portion comprised of one (in Tob55) or five (in BamA) polypeptide transport-associated (POTRA) domains. Currently the functional significance of this difference and whether the homology between BamA and Tob55 can allow them to replace each other are unclear. To address these issues we constructed hybrid Tob55/BamA proteins with differently configured N-terminal POTRA domains. We observed that constructs harboring a heterologous C-terminal domain could not functionally replace the bacterial BamA or the mitochondrial Tob55 demonstrating species-specific requirements. Interestingly, the various hybrid proteins in combination with the bacterial chaperones Skp or SurA supported to a variable extent the assembly of bacterial beta-barrel proteins into the mitochondrial OM. Collectively, our findings suggest that the membrane assembly of various beta-barrel proteins depends to a different extent on POTRA domains and periplasmic chaperones.

• 出版日期2016-12-16