AUTHOR=Galkina Kseniia V. , Zubareva Valeria M. , Kashko Nataliia D. , Lapashina Anna S. , Markova Olga V. , Feniouk Boris A. , Knorre Dmitry A. 

TITLE=Heterogeneity of Starved Yeast Cells in IF1 Levels Suggests the Role of This Protein in vivo

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.816622

DOI=10.3389/fmicb.2022.816622

ISSN=1664-302X

ABSTRACT=<p>In mitochondria, a small protein IF<sub>1</sub> suppresses the hydrolytic activity of ATP synthase and presumably prevents excessive ATP hydrolysis under conditions of energy deprivation. In yeast <italic>Saccharomyces cerevisiae</italic>, IF<sub>1</sub> homologs are encoded by two paralogous genes: <italic>INH1</italic> and <italic>STF1</italic>. <italic>INH1</italic> expression is known to aggravate the deleterious effects of mitochondrial DNA (mtDNA) depletion. Surprisingly, no beneficial effects of <italic>INH1</italic> and <italic>STF1</italic> were documented for yeast so far, and the functions of <italic>INH1</italic> and <italic>STF1</italic> in wild type cells are unclear. Here, we put forward a hypothesis that <italic>INH1</italic> and <italic>STF1</italic> bring advantage during the fast start of proliferation after reentry into exponential growth from post-diauxic or stationary phases. We found that yeast cells increase the concentration of both proteins in the post-diauxic phase. Post-diauxic phase yeast cells formed two subpopulations distinct in Inh1p and Stf1p concentrations. Upon exit from the post-diauxic phase cells with high level of Inh1-GFP started growing earlier than cells devoid of Inh1-GFP. However, double deletion of <italic>INH1</italic> and <italic>STF1</italic> did not increase the lag period necessary for stationary phase yeast cells to start growing after reinoculation into the fresh medium. These results point to a redundancy of the mechanisms preventing uncontrolled ATP hydrolysis during energy deprivation.</p>