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Cloning, expression, and chromosomal assignment of the human mitochondrial intermediate peptidase gene (MIPEP)
1Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Abstract:
The mitochondrial intermediate peptidase of Saccharomyces cerevisiae (YMIP) is a component of the yeast mitochondrial protein import machinery critically involved in the biogenesis of the oxidative phosphorylation (OXPHOS) system. This leader peptidase removes specific octapeptides from the amino terminus of nuclear-encoded OXPHOS subunits and components of the mitochondrial genetic apparatus. To address the biologic role of the human peptidase [MIPEP gene, HMIP polypeptide], we have initiated its molecular and functional characterization. A full-length cDNA was isolated by screening a human liver library using a rat MIP (RMIP) cDNA as a probe. The encoded protein contained a typical mitochondrial leader peptide and showed 92 and 54% homology to RMIP and YMIP, respectively. A survey of human mitochondrial protein precursors revealed that, similar to YMIP, HMIP is primarily involved in the maturation of OXPHOS-related proteins. Northern analysis showed that the MIPEP gene is differentially expressed in human tissues, with the highest levels of expression in the heart, skeletal muscle, and pancreas, three organ systems that are frequently affected in OXPHOS disorders. Using fluorescence in situ hybridization, the MIPEP locus was assigned to 13q12. This information offers the possibility of testing the potential involvement of HMIP in the pathophysiology of nuclear-driven OXPHOS disorders.
Insights
Human mitochondrial intermediate peptidase (HMIP) aids in oxidative phosphorylation (OXPHOS) protein maturation. Its gene (MIPEP) is expressed in key tissues, suggesting a role in OXPHOS disorders.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Biochemistry
Background:
- The mitochondrial intermediate peptidase (YMIP) is crucial for yeast oxidative phosphorylation (OXPHOS) system biogenesis.
- YMIP processes specific octapeptides from nuclear-encoded OXPHOS subunits.
Purpose of the Study:
- To characterize the molecular and functional aspects of the human homolog of YMIP, the human mitochondrial intermediate peptidase (HMIP).
- To investigate the role of HMIP in human mitochondrial protein processing and its potential involvement in OXPHOS disorders.
Main Methods:
- Isolation of full-length human MIPEP cDNA from a human liver library using a rat MIP (RMIP) cDNA probe.
- Sequence homology analysis comparing HMIP to RMIP and YMIP.
- Survey of human mitochondrial protein precursors for HMIP processing.
- Northern blot analysis to determine MIPEP gene expression patterns in human tissues.
- Fluorescence in situ hybridization (FISH) to map the MIPEP gene locus.
Main Results:
- HMIP shares significant homology with RMIP (92%) and YMIP (54%) and possesses a mitochondrial leader peptide.
- HMIP primarily processes OXPHOS-related proteins, similar to YMIP.
- MIPEP gene expression is highest in the heart, skeletal muscle, and pancreas.
- The MIPEP gene was localized to chromosome 13q12.
Conclusions:
- HMIP is the human counterpart of YMIP and plays a vital role in the maturation of OXPHOS proteins.
- Differential expression of MIPEP in tissues affected by OXPHOS disorders suggests HMIP's involvement in their pathophysiology.
- The localization of MIPEP provides a basis for investigating its role in nuclear-driven OXPHOS disorders.