Mitochondrial function in cell wall glycoprotein synthesis in Saccharomyces cerevisiae NCYC 625 (Wild type) and [rho(0)] mutants

Abstract

We studied phosphopeptidomannans (PPMs) of two Saccharomyces cerevisiae NCYC 625 strains (S. diastaticus): a wild type strain grown aerobically, anaerobically, and in the presence of antimycin and a [rho(0)] mutant grown aerobically and anaerobically. The aerobic wild-type cultures were highly flocculent, but all others were weakly flocculent. Ligands implicated in flocculation of mutants or antimycin-treated cells were not aggregated as much by concanavalin A as were those of the wild type. The [rho(0)] mutants and antimycin-treated cells differ from the wild type in PPM composition and invertase, acid phosphatase, and glucoamylase activities. PPMs extracted from different cells differ in the protein but not in the glycosidic moiety. The PPMs were less stable in mitochondrion-deficient cells than in wild-type cells grown aerobically, and this difference may be attributable to defective mitochondrial function during cell wall synthesis. The reduced flocculation of cells grown in the presence of antimycin, under anaerobiosis, or carrying a [rho(0)] mutation may be the consequence of alterations of PPM structures which are the ligands of lectins, both involved in this cell-cell recognition phenomenon. These respiratory chain alterations also affect peripheral, biologically active glycoproteins such as extracellular enzymes and peripheral PPMs.

FIG. 1

Growth curves of wild-type and [rho⁰] mutant S. cerevisiae NCYC 625 cells in aerobiosis, anaerobiosis, and anaerobiosis in the presence of antimycin. (A) Symbols: ◊, □, and ●, wild-type cells grown in aerobiosis, anaerobiosis, and aerobiosis in the presence of antimycin, respectively. (B) Symbols: ×, mA; ○, mN; [rho⁰] mutant cells grown in aerobiosis and anaerobiosis, respectively; ↑, cell harvesting time for PPM extraction.

FIG. 2

Amino acid composition profiles of PPMs of wild-type and [rho⁰] mutant S. cerevisiae NCYC 625. Symbols: □ and , wild-type cells grown in aerobiosis and anaerobiosis, respectively;  and , [rho⁰] mutant cells grown in aerobiosis and anaerobiosis, respectively. Results are expressed as percentages of the total amino acid content.

FIG. 3

Amino acid composition profiles of peaks I and II obtained after mercaptoethanol treatment of PPMs extracted from wild-type or [rho⁰] mutant S. cerevisiae NCYC 625 grown in aerobiosis. Symbols: □ and , wild-type and [rho⁰] mutant cells grown in aerobiosis, respectively. Results are expressed as percentages of the total amino acid content.