The role of amino acids in the transmembrane and extra-membranous domains of the S. cerevisiae iron sulfur protein in its activity and stability in the cytochrome bc1 complex.

摘要

It is hypothesized that electron transfer by the iron sulfur protein requires movement of a flexible "tether" region that connects the transmembrane portion of the protein to its extramembranous domain. To determine which amino acid residues are important for catalysis and stability of the Saccharomyces cerevisiae iron sulfur protein, site-directed mutagenesis was performed on two charged residues adjacent to the proposed flexible region.;When these mutant yeast cells were grown at 37°C, the growth of the both the K93L and E95R cells were decreased, as was the enzymatic activity. No reduction of cytochromes b or c1 was observed in these cells; however, the level of iron sulfur protein was decreased, suggesting that these charged residues are not required for proper function of the iron sulfur protein at 30°C, but may be important for the stability of the protein when the yeast are grown at nonpermissive temperatures. (Abstract shortened by UMI.)