The putative membrane anchor protein for yeast Sec7p recruitment

Proteins required for yeast secretory pathway function have been identified by genetic selection and characterization of the temperature-sensitive secretory (sec) mutants. The use of genetic and biochemical approaches has expanded the catalog of components of the secretory pathway, yet many proteins, especially membrane and lumenal proteins, remain to be identified. Sec7p, one of the original SEC gene products to be described, is required at multiple stages of the yeast secretory pathway in the coating of transport vesicles. A chemical cross-linking approach was used to identify proteins associated with Sec7p protein complexes from yeast cell lysates. A 90 kDa integral membrane protein (p90) was isolated whose interactions with Sec7p were reproduced in the absence of chemical cross-linking. Further biochemical analysis indicated that p90 may act as the anchor protein for Sec7p membrane recruitment in transport vesicle assembly.