ARS | Publication request: Distinct Pathways Mediate the Sorting of Tail-anchored Mitochondrial Outer Membrane Proteins

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2009
Publication Date: December 4, 2009
Citation: Marty, N.J., Hwang, Y.T., Zhang, D., Dyer, J.M., and Mullen, R.T. (2009). Distinct Pathways Mediate the Sorting of Tail-anchored Mitochondrial Outer Membrane Proteins. Eastern Regional Meeting of the Canadian Society of Plant Physiologists, December 4 - 5, 2009, Guelph, Ontario, Canada.

Technical Abstract: Little is known about the biogenesis of tail-anchored (TA) proteins localized to the mitochondrial outer membrane in plant cells. To address this issue, we screened all of the (>500) known and predicted TA proteins in Arabidopsis for those annotated, based on Gene Ontology, to possess mitochondrial-related function(s) and/or contain a C-terminal sequence resembling the targeting signal motif characterized previously for mitochondrial isoforms of the TA protein cytochrome b5 (Cb5). Surprisingly, only two of the ~30 TA proteins annotated as mitochondrial possessed a Cb5-like targeting signal. Using tobacco BY-2 cells as a model in vivo targeting system we confirmed the mitochondrial localization and TA topology for several members of each group of proteins, and subsequent mutagenic analyses revealed that their C termini, while perceptively different at the primary sequence level, were both necessary and sufficient for mitochondrial targeting. We also employed split-YFP assays to show that while both groups of TA proteins interact with certain components of the translocase of the mitochondrial outer membrane (TOM), only a few TA proteins interact also with the sorting and assembly machinery (SAM). Collectively, these results in combination with other findings suggest that mitochondrial TA proteins rely on several different and possibly parallel pathways.