PROTEIN TRANSLOCATION AND PROCESSING IN OVIDUCT

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This is a proposal to undertake a study of hen oviduct signal peptidase, a membrane-bound proteinase that removes amino-terminal signal peptides from nascent secretory precursor proteins. The enzyme will be purified and characterized biochemically. This proteinase is representative of a number of highly-specific enzymes involved in a variety of cellular processing events such as activation of hormone precursors and zymogens, excision of biologically-active peptides from multifunctional precursors, and transport of cytoplasmically-synthesized proteins into mitochondria and chloroplasts. An improved assay for signal peptidase activity will be developed that will aid its isolation and characterization. Specific inhibitors of the enzyme will be developed to characterize its mechanistic class and to probe its role in the transport process. Hen oviduct signal recognition particle, a complex of protein and RNA that recognizes ribosomes synthesizing secretory proteins and causes them to attach to transport sites on the endoplasmic reticulum, will be identified, isolated, and used to study the mechanism of secretion of ovalbumin in its homologous tissue. An antibody specific for the signal peptide of human pre-placental lactogen will be prepared and used to explore the role of the signal peptide in the protein transport process. A long-term goal of this study is to separate the components required for transport of secretory proteins into the endoplasmic reticulum and reconstitute them into artificial liposomes in a functional manner. Such a reconstituted system will lead to a detailed understanding of the mechanism by which cells synthesize and transport secretory proteins.