Protein Translocation in Yeast

Walter, Peter

Abstract

The primary objective of the proposed research is to understand the mechanism by which the correct proteins are targeted to and translocated across the endoplasmic reticulum membrane in the simple eucaryote Saccharomyces cerevisiae. Current models suggest that there are at least two parallel targeting and translocation pathways, one SRP-dependent and co-translational, the other SRP-independent and post-translational. Through the combination of genetic and biochemical approaches, we aim to identify the gene products that catalyze the reactions that are common to both pathways or unique to one or the other and to understand their molecular function, regulation and physiological importance. Specifically, i) we will characterize the mechanism(s) by which SRP and SRP receptor coordinate the interactions between the ribosome and translocon components to form the ribosome membrane junction. ii) We will characterize the components that mediate the SRP-independent pathway. We will analyze how these components function to select proteins into this pathway, and how they function to target proteins to the ER membrane. iii) We will determine the molecular basis of """"""""adaptation"""""""", the physiological response that allows cells to improve protein translocation when the SRP-dependent pathway is disrupted. We wish to learn which aspects of the process are unique to yeast and which aspects can be generalized to other eucaryotic cells and bacteria. Ultimately, we hope that through a combined genetic and biochemical approach, we will understand, at a mechanistic level, the function of all of the cellular constituents of the protein translocation machinery that are essential for translocation, as well as the function of those that are modulatory.