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Publication Abstract from PubMed

In mitochondria, beta-barrel outer membrane proteins mediate protein import, metabolite transport, lipid transport, and biogenesis. The Sorting and Assembly Machinery (SAM) complex consists of three proteins that assemble as a 1:1:1 complex to fold beta-barrel proteins and insert them into the mitochondrial outer membrane. We report cryoEM structures of the SAM complex from Myceliophthora thermophila, which show that Sam50 forms a 16-stranded transmembrane beta-barrel with a single polypeptide-transport-associated (POTRA) domain extending into the intermembrane space. Sam35 and Sam37 are located on the cytosolic side of the outer membrane, with Sam35 capping Sam50, and Sam37 interacting extensively with Sam35. Sam35 and Sam37 each adopt a GST-like fold, with no functional, structural, or sequence similarity to their bacterial counterparts. Structural analysis shows how the Sam50 beta-barrel opens a lateral gate to accommodate its substrates.

Structural insight into mitochondrial beta-barrel outer membrane protein biogenesis.,Diederichs KA, Ni X, Rollauer SE, Botos I, Tan X, King MS, Kunji ERS, Jiang J, Buchanan SK Nat Commun. 2020 Jul 3;11(1):3290. doi: 10.1038/s41467-020-17144-1. PMID:32620929^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.