- Autor(in)
- Seitenbereich
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538-550
- Zusammenfsg.
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The mitochondrial DNA of yeast (Saccharomyces cerevisiae) contains repetitive GC rich elements among the AT-rich non-coding sequences between the genes. Based on their primary structure, these GC clusters are subdivided into various groups of which one group comprising GC clusters of 44 bp in length is both, very highly conserved and very frequent. Using gel mobility shift assays we show that this 44 bp GC cluster is capable of forming two specific DNA/protein complexes with a soluble mitochondrial protein extract. The protein responsible for the larger complex was isolated by affinity chromatography and identified as the mitochondrial serine hydroxymethyl-transferase (SHMT). The analysis of a deletion mutant of this enzyme provided evidence for a direct interaction between the DNA and the SHMT. The binding is dependent on the primary sequence rather than on secondary stem-loop structures. SHMT normally catalyzes the reversible transfer of C1 residues to tetrahydrofolate by the interconversion of serine and glycine. We propose that the serine hydroxymethyltransferase is a bifunctional enzyme with roles in metabolism as well as in mitochondrial genome organization.