Poster abstracts

Poster number 61 submitted by Seth Hennon

Flexibility and proximity relationships between the TM segments of the E. coli YidC

Seth W. Hennon (Department of Chemistry and Biochemistry at The Ohio State University), Ross E. Dalbey (Department of Chemistry and Biochemistry at The Ohio State University)

Abstract:
The YidC family members function to insert proteins into membranes in bacteria, chloroplasts, and mitochondria and they can also act as a platform to fold and assemble proteins into higher order complexes. Here, we provide information about the proximity relationships and dynamics of the five conserved C-terminal transmembrane (TM) regions within E. coli YidC. By using a YidC construct, with tandem thrombin protease sites introduced into the cytoplasmic loop C1, crosslinking between paired-Cys residues located within TM segments or in the membrane border regions was studied using thiospecific homobifunctional crosslinking agents with different spanner lengths or by iodine-catalyzed disulfide formation. These crosslinking studies show that TM3, TM4, TM5, and TM6 each have a face oriented toward TM2 of the in vivo expressed YidC. The studies also reveal that YidC is a dynamic protein, as crosslinking was observed between cytoplasmic Cys residues with a variety of crosslinkers. A large number of conserved proline residues on the cytoplasmic side of the 5 conserved core TM segments could explain the observed flexibility and the structural fluctuations of the TM segments could provide an explanation of how YidC is able to recognize a variety of different substrates.

Keywords: YidC, Cysteine Crosslinking, Helical Packing