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Mitochondrial receptor complex protein. The intermembrane space domain of yeast MAS17 is not essential for its
1Department of Chemistry, Faculty of Science, Nagoya University, Japan.
Abstract:
MAS17 (MAS22) is an essential component of the import receptor complex in the yeast mitochondrial outer membrane. MAS17 consists of three distinct domains: the N-terminal cytosolic domain, the internal membrane-spanning domain, and the C-terminal intermembrane space domain. In the present study, we examined the roles of the C-terminal domain of MAS17, which is rich in acidic amino acids, in protein import into mitochondria both in vivo and in vitro. Cells expressing MAS17 delta 120-152, a mutant MAS17 lacking the C-terminal acidic domain, could grow as fast as those expressing wild-type MAS17, while cells expressing MAS17 delta 97-152, a mutant MAS17 lacking both the intermembrane space and the membrane-spanning domains, stopped growing as soon as wild-type MAS17 was depleted. MAS17 delta 120-152 was correctly integrated into the mitochondrial outer membrane like wild-type MAS17. Mitochondria containing MAS17 delta 120-152 instead of wild-type MAS17 could import both authentic and artificial mitochondrial precursor proteins nearly as efficiently as wild-type mitochondria in vitro. These results suggest that the C-terminal intermembrane space domain of MAS17 is not essential for targeting or functions of MAS17.
Insights
The C-terminal domain of MAS17 (MAS22) is not essential for yeast mitochondrial protein import. Deleting this acidic region did not affect cell growth or protein import efficiency.
Area of Science:
- Mitochondrial Biology
- Protein Import
- Cellular Biology
Background:
- MAS17 (MAS22) is a crucial component of the yeast mitochondrial outer membrane's import receptor complex.
- MAS17 possesses three domains: N-terminal cytosolic, internal membrane-spanning, and C-terminal intermembrane space.
Purpose of the Study:
- To investigate the role of the acidic C-terminal domain of MAS17 in mitochondrial protein import.
- To determine if this domain is essential for MAS17 targeting and function.
Main Methods:
- In vivo growth assays of yeast strains expressing wild-type and mutant MAS17.
- In vitro mitochondrial protein import assays using isolated mitochondria.
- Analysis of MAS17 mutant integration into the mitochondrial outer membrane.
Main Results:
- Yeast expressing MAS17 lacking the C-terminal acidic domain (MAS17 delta 120-152) exhibited normal growth.
- Mitochondria with MAS17 delta 120-152 efficiently imported precursor proteins in vitro.
- A mutant lacking both intermembrane space and membrane-spanning domains (MAS17 delta 97-152) impaired growth.
Conclusions:
- The C-terminal intermembrane space domain of MAS17 is not essential for its targeting to the mitochondrial outer membrane.
- This domain is dispensable for the function of MAS17 in mitochondrial protein import.