2011 OSU Molecular Life Sciences
Interdisciplinary Graduate Programs Symposium

 

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Poster number 47 submitted by Raunak Soman

Certain Procoat mutants with mutations in the periplasmic region are routed to the SecYEG translocase in the presence of SecA

Raunak J Soman (Department of Chemistry/Ohio State Biochemistry Program, The Ohio State University, Columbus OH 43210), Jijun Yuan (Department of Chemistry/ Ohio State Biochemistry Program, The Ohio State University, Columbus OH 43210), Andreas Kuhn (Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599, Stuttgart, Germany), Ross E. Dalbey (The Department of Chemistry, The Ohio State University, Columbus OH 43210)

Abstract:
M13 procoat is the major coat protein of the M13 phage and was initially thought to spontaneously insert into the membrane during phage infection. In the year 2000 it was shown that a new inner membrane protein YidC is involved in inserting it into the membrane. Further studies have shown that small changes to the periplasmic loop of procoat can cause it to be inserted by the SecYEG pathway (the major pathway for inner membrane protein insertion and export across the membrane in bacteria) instead of the YidC pathway.

In this study, we test the hypothesis that SecA functions as a targeting factor and that it is SecA which determines that proteins such as the -3M (containing 3 negative charges in the middle of the periplasmic loop) and -5 procoat (containing a total of 5 negative charges in the periplasmic loop) require SecYEG for insertion. In cells depleted of SecA, then the -3M and -5 procoat proteins can insert efficiently into the membrane, as they are not routed to the Sec translocase. To confirm this result, we show that the -3M and -5 procoat proteins can insert efficiently into cells depleted of SecE. In vivo photocrosslinking is in progress to map out the insertion pathway in detail by identifying the protein components that -5 procoat interacts with while it is inserting into the membrane and this result will be compared to wildtype procoat.

Keywords: YidC, Procoat, Membrane Protein Insertion