scholarly journals RPM2, independently of its mitochondrial RNase P function, suppresses an ISP42 mutant defective in mitochondrial import and is essential for normal growth.

1995 ◽  
Vol 15 (9) ◽  
pp. 4763-4770 ◽  
Author(s):  
C K Kassenbrock ◽  
G J Gao ◽  
K R Groom ◽  
P Sulo ◽  
M G Douglas ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Normal Growth ◽  
Rnase P ◽  
Growth Defect ◽  
Temperature Sensitive ◽  
Mitochondrial Trna ◽  
Mitochondrial Protein Import ◽  
Established Role ◽  
Fermentative Yeast

RPM2 is identified here as a high-copy suppressor of isp42-3, a temperature-sensitive mutant allele of the mitochondrial protein import channel component, Isp42p. RPM2 already has an established role as a protein component of yeast mitochondrial RNase P, a ribonucleoprotein enzyme required for the 5' processing of mitochondrial precursor tRNAs. A relationship between mitochondrial tRNA processing and protein import is not readily apparent, and, indeed, the two functions can be separated. Truncation mutants lacking detectable RNase P activity still suppress the isp42-3 growth defect. Moreover, RPM2 is required for normal fermentative yeast growth, even though mitochondrial RNase P activity is not. The portion of RPM2 required for normal growth and suppression of isp42-3 is the same. We conclude that RPM2 is a multifunctional gene. We find Rpm2p to be a soluble protein of the mitochondrial matrix and discuss models to explain its suppression of isp42-3.

scholarly journals MAS6 encodes an essential inner membrane component of the yeast mitochondrial protein import pathway

1993 ◽  
Vol 122 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
JL Emtage ◽  
RE Jensen
Keyword(s):  
Protein Import ◽  
Early Stage ◽  
Osmotic Shock ◽  
Alkali Treatment ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane

To identify new components that mediate mitochondrial protein import, we analyzed mas6, an import mutant in the yeast Saccharomyces cerevisiae. mas6 mutants are temperature sensitive for viability, and accumulate mitochondrial precursor proteins at the restrictive temperature. We show that mas6 does not correspond to any of the presently identified import mutants, and we find that mitochondria isolated from mas6 mutants are defective at an early stage of the mitochondrial protein import pathway. MAS6 encodes a 23-kD protein that contains several potential membrane spanning domains, and yeast strains disrupted for MAS6 are inviable at all temperatures and on all carbon sources. The Mas6 protein is located in the mitochondrial inner membrane and cannot be extracted from the membrane by alkali treatment. Antibodies to the Mas6 protein inhibit import into isolated mitochondria, but only when the outer membrane has been disrupted by osmotic shock. Mas6p therefore represents an essential import component located in the mitochondrial inner membrane.

scholarly journals MAS5, a yeast homolog of DnaJ involved in mitochondrial protein import.

1992 ◽  
Vol 12 (1) ◽  
pp. 283-291 ◽  
Author(s):  
D P Atencio ◽  
M P Yaffe
Keyword(s):  
Protein Import ◽  
Elevated Temperatures ◽  
Mitochondrial Protein ◽  
Heat Shock Gene ◽  
Temperature Sensitive ◽  
Mitochondrial Protein Import ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mutant Phenotypes ◽  
Cloned Gene ◽  
Yeast Homolog

The nuclear mas5 mutation causes temperature-sensitive growth and defects in mitochondrial protein import at the nonpermissive temperature in the yeast Saccharomyces cerevisiae. The MAS5 gene was isolated by complementation of the mutant phenotypes, and integrative transformation demonstrated that the complementing fragment encoded the authentic MAS5 gene. The deduced protein sequence of the cloned gene revealed a polypeptide of 410 amino acids which is homologous to Escherichia coli DnaJ and the yeast DnaJ log SCJ1. Northern (RNA blot) analysis revealed that MAS5 is a heat shock gene whose expression increases moderately at elevated temperatures. Cells with a deletion mutation in MAS5 grew slowly at 23 degrees C and were inviable at 37 degrees C, demonstrating that MAS5 is essential for growth at increased temperatures. The deletion mutant also displayed a modest import defect at 23 degrees C and a substantial import defect at 37 degrees C. These results indicate a role for a DnaJ cognate protein in mitochondrial protein import.

A mutation in the yeast heat-shock factor gene causes temperature-sensitive defects in both mitochondrial protein import and the cell cycle

1991 ◽  
Vol 11 (5) ◽  
pp. 2647-2655 ◽  
Author(s):  
B J Smith ◽  
M P Yaffe
Keyword(s):  
Cell Cycle ◽  
Heat Shock ◽  
Cell Cycle Progression ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Yeast Cells ◽  
Heat Shock Gene ◽  
Temperature Sensitive ◽  
Mitochondrial Protein Import ◽  
Cycle Progression

Yeast cells containing the recessive mas3 mutation display temperature-sensitive defects in both mitochondrial protein import and the cell division cycle. The import defect is characterized by two pools of mitochondrial precursors and a dramatically slower rate of posttranslational import. The effect of mas3 on cell cycle progression occurs within one cell cycle at the nonpermissive temperature and retards progression through the G2 stage. The mas3 mutation maps to the gene encoding yeast heat-shock transcription factor (HSF), and expression of wild-type HSF complements the temperature-sensitive defects. The mas3 lesion has no apparent effect on protein secretion. In mas3 cells, induction of a major heat-shock gene, SSA1, is defective at 37 degrees C. The properties of the mas3 mutant cells indicate that HSF mediates the response to stress of two basic cellular processes: mitochondrial protein import and cell cycle progression.

scholarly journals A mutation in the yeast heat-shock factor gene causes temperature-sensitive defects in both mitochondrial protein import and the cell cycle.

1991 ◽  
Vol 11 (5) ◽  
pp. 2647-2655 ◽  
Author(s):  
B J Smith ◽  
M P Yaffe
Keyword(s):  
Cell Cycle ◽  
Heat Shock ◽  
Cell Cycle Progression ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Yeast Cells ◽  
Heat Shock Gene ◽  
Temperature Sensitive ◽  
Mitochondrial Protein Import ◽  
Cycle Progression

Yeast cells containing the recessive mas3 mutation display temperature-sensitive defects in both mitochondrial protein import and the cell division cycle. The import defect is characterized by two pools of mitochondrial precursors and a dramatically slower rate of posttranslational import. The effect of mas3 on cell cycle progression occurs within one cell cycle at the nonpermissive temperature and retards progression through the G2 stage. The mas3 mutation maps to the gene encoding yeast heat-shock transcription factor (HSF), and expression of wild-type HSF complements the temperature-sensitive defects. The mas3 lesion has no apparent effect on protein secretion. In mas3 cells, induction of a major heat-shock gene, SSA1, is defective at 37 degrees C. The properties of the mas3 mutant cells indicate that HSF mediates the response to stress of two basic cellular processes: mitochondrial protein import and cell cycle progression.

MAS5, a yeast homolog of DnaJ involved in mitochondrial protein import

1992 ◽  
Vol 12 (1) ◽  
pp. 283-291
Author(s):  
D P Atencio ◽  
M P Yaffe
Keyword(s):  
Protein Import ◽  
Elevated Temperatures ◽  
Mitochondrial Protein ◽  
Heat Shock Gene ◽  
Temperature Sensitive ◽  
Mitochondrial Protein Import ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mutant Phenotypes ◽  
Cloned Gene ◽  
Yeast Homolog

The nuclear mas5 mutation causes temperature-sensitive growth and defects in mitochondrial protein import at the nonpermissive temperature in the yeast Saccharomyces cerevisiae. The MAS5 gene was isolated by complementation of the mutant phenotypes, and integrative transformation demonstrated that the complementing fragment encoded the authentic MAS5 gene. The deduced protein sequence of the cloned gene revealed a polypeptide of 410 amino acids which is homologous to Escherichia coli DnaJ and the yeast DnaJ log SCJ1. Northern (RNA blot) analysis revealed that MAS5 is a heat shock gene whose expression increases moderately at elevated temperatures. Cells with a deletion mutation in MAS5 grew slowly at 23 degrees C and were inviable at 37 degrees C, demonstrating that MAS5 is essential for growth at increased temperatures. The deletion mutant also displayed a modest import defect at 23 degrees C and a substantial import defect at 37 degrees C. These results indicate a role for a DnaJ cognate protein in mitochondrial protein import.

scholarly journals Identification of Tam41 maintaining integrity of the TIM23 protein translocator complex in mitochondria

2006 ◽  
Vol 174 (5) ◽  
pp. 631-637 ◽  
Author(s):  
Yasushi Tamura ◽  
Yoshihiro Harada ◽  
Koji Yamano ◽  
Kazuaki Watanabe ◽  
Daigo Ishikawa ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Molecular Size ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Protein Import ◽  
The Matrix

Newly synthesized mitochondrial proteins are imported into mitochondria with the aid of protein translocator complexes in the outer and inner mitochondrial membranes. We report the identification of yeast Tam41, a new member of mitochondrial protein translocator systems. Tam41 is a peripheral inner mitochondrial membrane protein facing the matrix. Disruption of the TAM41 gene led to temperature-sensitive growth of yeast cells and resulted in defects in protein import via the TIM23 translocator complex at elevated temperature both in vivo and in vitro. Although Tam41 is not a constituent of the TIM23 complex, depletion of Tam41 led to a decreased molecular size of the TIM23 complex and partial aggregation of Pam18 and -16. Import of Pam16 into mitochondria without Tam41 was retarded, and the imported Pam16 formed aggregates in vitro. These results suggest that Tam41 facilitates mitochondrial protein import by maintaining the functional integrity of the TIM23 protein translocator complex from the matrix side of the inner membrane.

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