The molecular events involved in the translocation of a protein through a biological membrane and the components which mediate this process are just being defined in different membrane systems. Recent advances in the analysis of the mitochondrial import pathway in yeast now provide a well defined system in which detailed biochemical and genetic analysis is possible. The level of molecular analysis defined in the proposed studies should provide new insights into the general problem of intracellular protein transport. Our studies and those of others have demonstrated that the mitochondrial import apparatus consists of components which recognize unique structural features of a mitochondrial import signal as well as an apparatus for reorginization of protein structure to initiate or maintain the import process. The proposed studies in yeast, Saccharomyces cerevisiae will utilize the combination of biochemical fractionation and genetic analysis to define the mitochondrial and cellular components which participate in the reorganization and translocation of mitochondrial precursors from the cytoplasm. Components of the mitochondrial import site will be isolated and characterized by taking advantage of the copurification of translocation intermediates and hybrid mitochondrial precursors which have initiated but not completed protein import. Components of the import site which mediate the unfolding or reorganization of mitochondrial precursors on the mitochondrial surface will be purified using a protein unfolding assay. In all cases isolated components will be used to prepare specific immunological and genetic probes for in vitro and in vivo studies. The yeast mutant MAD1 which exhibits a conditional block in protein import will be further characterized to define its position in the import apparatus and to select pseudorevertants which genetically uncover other components of the import pathway. These pseudorevertants as well as probes obtained by the biochemical approach should facilitate our understanding of the molecular events of protein sorting and transport.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM036537-06
Application #
3290700
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1989-09-01
Project End
1993-11-30
Budget Start
1989-12-01
Budget End
1990-11-30
Support Year
6
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Type
Schools of Medicine
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Kassenbrock, C K; Cao, W; Douglas, M G (1993) Genetic and biochemical characterization of ISP6, a small mitochondrial outer membrane protein associated with the protein translocation complex. EMBO J 12:3023-34
Yuan, H; Douglas, M G (1992) The mitochondrial F1ATPase alpha-subunit is necessary for efficient import of mitochondrial precursors. J Biol Chem 267:14697-702
Cyr, D M; Lu, X; Douglas, M G (1992) Regulation of Hsp70 function by a eukaryotic DnaJ homolog. J Biol Chem 267:20927-31
Cyr, D M; Douglas, M G (1991) Early events in the transport of proteins into mitochondria. Import competition by a mitochondrial presequence. J Biol Chem 266:21700-8
Hoyt, D W; Cyr, D M; Gierasch, L M et al. (1991) Interaction of peptides corresponding to mitochondrial presequences with membranes. J Biol Chem 266:21693-9
Smagula, C; Douglas, M G (1988) Mitochondrial import of the ADP/ATP carrier protein in Saccharomyces cerevisiae. Sequences required for receptor binding and membrane translocation. J Biol Chem 263:6783-90
Chen, W J; Douglas, M G (1988) An F1-ATPase beta-subunit precursor lacking an internal tetramer-forming domain is imported into mitochondria in the absence of ATP. J Biol Chem 263:4997-5000
Vassarotti, A; Chen, W J; Smagula, C et al. (1987) Sequences distal to the mitochondrial targeting sequences are necessary for the maturation of the F1-ATPase beta-subunit precursor in mitochondria. J Biol Chem 262:411-8
Chen, W J; Douglas, M G (1987) Phosphodiester bond cleavage outside mitochondria is required for the completion of protein import into the mitochondrial matrix. Cell 49:651-8
Chen, W J; Douglas, M G (1987) The role of protein structure in the mitochondrial import pathway. Unfolding of mitochondrially bound precursors is required for membrane translocation. J Biol Chem 262:15605-9

Showing the most recent 10 out of 12 publications