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Two inactive fragments derived from the yeast mitochondrial ribosomal protein MrpS28 function in trans to support
M O Huff1, P J Hanic-Joyce, H Dang
1Department of Biochemistry, University of Louisville, Kentucky 40292.
Abstract:
The mitochondrial ribosomal protein MrpS28 of Saccharomyces cerevisiae is one of several mitochondrial ribosomal proteins homologous to Escherichia coli ribosomal proteins within the context of a larger protein. Relative to a region of homology with E. coli ribosomal protein S15, the mature MrpS28 protein has unique sequence domains of 117 and 48 amino acids at its amino and carboxyl terminus, respectively. To better understand the role of the various sequence domains of the MrpS28 protein in vivo, truncated derivatives were expressed under conditions where they were the only potential source of functional MrpS28 protein. The results shown here demonstrate that the amino-terminal domain and the S15-like domain are both essential for respiratory growth. Interestingly an inactive amino-terminal fragment can be complemented in trans by a second inactive fragment comprising the S15-like domain and the carboxyl-terminal 48 amino acids. Consequently, the assembly of these fragments into ribosomal subunits can be examined when they are expressed individually or together. Results from these studies indicate that each of the MrpS28-derived fragments facilitates the incorporation of the other into 37 S ribosomal subunits.
Insights
The amino-terminal and S15-like domains of Saccharomyces cerevisiae mitochondrial ribosomal protein MrpS28 are crucial for respiratory growth. These domains can functionally complement each other in trans for ribosomal subunit assembly.
Area of Science:
- Mitochondrial biology
- Ribosome biogenesis
- Molecular genetics
Background:
- Mitochondrial ribosomal protein MrpS28 in Saccharomyces cerevisiae shares homology with Escherichia coli ribosomal protein S15.
- Mature MrpS28 contains unique amino-terminal (117 amino acids) and carboxyl-terminal (48 amino acids) domains beyond the S15-homologous region.
Purpose of the Study:
- To investigate the in vivo functional roles of distinct sequence domains within the MrpS28 protein.
- To determine the necessity of each domain for essential cellular processes like respiratory growth.
Main Methods:
- Expression of truncated MrpS28 derivatives in yeast lacking functional endogenous MrpS28.
- Assessment of respiratory growth in yeast strains expressing these truncated proteins.
- Analysis of ribosomal subunit assembly using expressed MrpS28 fragments.
Main Results:
- Both the amino-terminal and S15-like domains of MrpS28 are essential for supporting respiratory growth.
- An inactive amino-terminal fragment can be functionally complemented by a fragment containing the S15-like and carboxyl-terminal domains.
- Individual MrpS28-derived fragments facilitate the incorporation of each other into 37S ribosomal subunits.
Conclusions:
- The distinct domains of MrpS28 play critical, non-redundant roles in mitochondrial function and ribosome assembly.
- Functional complementation between MrpS28 fragments provides insights into the modular nature of ribosomal protein function.
- These findings contribute to understanding the intricate process of mitochondrial ribosome biogenesis.