Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

14-POS Board 4 TOWARDS MECHANISTIC UNDERSTANDING OF MITOCHONDRIAL BETA- BARREL BIOGENESIS: FUNCTIONAL STUDIES OF THE SORTING AND ASSEMBLY MACHINERY COMPLEX Kathryn A Diederichs 1 ; Sarah E Rollauer 1 ; Martin S King 3 ; Edmund R.S. Kunji 3 ; Joseph A Mindell 2 ; Susan K Buchanan 1 ; 3 University of Cambridge, MRC Mitochondrial Biology Unit, Cambridge, United Kingdom The mitochondrial outer membrane of yeast contains four types of beta-barrel proteins (Sam50, Tom40, Mdm10, and VDAC), all of which are translated in the cytosol and imported into the mitochondria as unfolded precursors. The sorting and assembly machinery (SAM) complex recognizes beta-barrel precursors by a conserved C-terminal sequence motif, the beta-signal, and facilitates their folding and insertion into the outer membrane. The SAM complex is composed of three subunits: Sam50, Sam35, and Sam37. Sam50 and Sam35 are essential for cell viability and beta-barrel biogenesis, and have been demonstrated to specifically interact with precursor beta-signal. However, the molecular mechanisms of SAM complex beta-signal recognition, precursor folding, and membrane insertion are currently unknown. We previously solved a high- resolution cryo-electron microscopy structures of the SAM complex from the fungi Thermothelomyces thermophilus. Current work uses these structures to design experiments that will characterize the interaction of the SAM complex subunits with beta-signal and beta-barrel precursors as they fold using a variety of biochemical and biophysical techniques. Ultimately, this work will improve mechanistic understanding of SAM complex function and mitochondrial outer membrane beta-barrel biogenesis. 1 NIH, NIDDK, Bethesda, MD, USA 2 NIH, NINDS, Bethesda, MD, USA

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