UNIVERSITY OF MASSACHUSETTS
The rough endoplasmic reticulum is a major site of protein synthesis in eukaryotic cells, serving as the entry point for the secretory pathway, and the biosynthetic site for the majority of cellular integral membrane proteins. The long-term goal of the parent proposal is to elucidate the mechanism of protein translocation and membrane protein integration. The three specific aims of the parent proposal were to analyze the signal recognition particle (SRP) and SRP receptor-dependent steps in the translocation reaction that culminate with the selective attachment of a ribosome-nascent chain complex (RNC) to the translocation channel, (b) to investigate the in vivo kinetics of membrane protein integration in S. cerevisiae using ubiquitin-translocation assay (UTA) reporters, and (c) to conduct a structure-function analysis of the yeast protein translocation channels using the M. jannaschii SecYE? structure as a guide to design informative mutants. The objective of this supplement is to complete two projects that fall within the second and third specific aims of the parent proposal.