The Origin of Mitochondria-Specific Outer Membrane ?-Barrels from an Ancestral Bacterial Fragment.

ABSTRACT: Outer membrane ?-barrels (OMBBs) are toroidal arrays of antiparallel ?-strands that span the outer membrane of Gram-negative bacteria and eukaryotic organelles. Although homologous, most families of bacterial OMBBs evolved through the independent amplification of an ancestral ??-hairpin. In mitochondria, one family (SAM50) has a clear bacterial ancestry; the origin of the other family, consisting of 19-stranded OMBBs found only in mitochondria (MOMBBs), is substantially unclear. In a large-scale comparison of mitochondrial and bacterial OMBBs, we find evidence that the common ancestor of all MOMBBs emerged by the amplification of a double ??-hairpin of bacterial origin, probably at the time of the Last Eukaryotic Common Ancestor. Thus, MOMBBs are indeed descended from bacterial OMBBs, but their fold formed independently in the proto-mitochondria, possibly in response to the need for a general-purpose polypeptide importer. This occurred by a process of amplification, despite the final fold having a prime number of strands.

SUBMITTER: Pereira J 

PROVIDER: S-EPMC6193526 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature