title: Disruption of the gene for Hsp30, an alpha-crystallin-related heat shock protein of Neurospora crassa, causes defects in import of proteins into mitochondria.
abstract: The gene for Hsp30, the only known alpha-crystallin-related heat shock protein of Neurospora crassa, was disrupted by repeat-induced point mutagenesis, leading to loss of cell survival at high temperature. Hsp30, which is not synthesized at 30 degrees C, associates reversibly with the mitochondria at high temperature (45 degrees C). In this study, we found that import of selected proteins into internal compartments of mitochondria, following their synthesis in the cytosol, was severely impaired at high temperature in a strain mutant in Hsp30. After 70 min of cell incubation at 45 degrees C, most matrix, inner membrane, and intermembrane-space proteins tested were reduced in import by about 50-70% in the mutant, as compared to wild-type cells. In contrast, assembly of selected proteins into the outer mitochondrial membrane was not reduced, except for one component of the preprotein translocase complex of the mitochondrial outer membrane. Three proteins of this complex co-immunoprecipitated with Hsp30 of wild-type cells incubated at 45 degrees C. We propose that Hsp30 interacts with the preprotein translocase of the mitochondrial outer membrane and that it chaperones the activity of one or more components of this translocase complex at high temperature.
authors.affiliation: Department of Plant Biology, The University of Minnesota, Saint Paul 55108, USA.
authors.forename: N
authors.initials: N
authors.lastname: Plesofsky
authors.forename: N
authors.initials: N
authors.lastname: Gardner
authors.forename: R
authors.initials: R
authors.lastname: Lill
authors.forename: R
authors.initials: R
authors.lastname: Brambl
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D029968:Escherichia coli Proteins; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D050890:HSP30 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D009492:Neurospora crassa / Q000235:genetics* / Q000378:metabolism; D019696:Peptidylprolyl Isomerase / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003574:Cytochrome c Group; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; D050890:HSP30 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D003576:Electron Transport Complex IV; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; D019696:Peptidylprolyl Isomerase; D000081416:SecA Proteins