A glycolytic metabolon in Saccharomyces cerevisiae isstabilized by F-actin

摘要

In the Saccharomyces cerevisiae glycolytic pathway, 11 enzymes catalyzethe stepwise conversion of glucose to two molecules of ethanol plus twoCO2 molecules. In the highly crowded cytoplasm, this pathway would bevery inefficient if it were dependent on substrate/enzyme diffusion. Therefore, the existence of a multi-enzymatic glycolytic complex has been suggested. This complex probably uses the cytoskeleton to stabilize theinteraction of the various enzymes. Here, the role of filamentous actin(F-actin) in stabilization of a putative glycolytic metabolon is reported.Experiments were performed in isolated enzyme/actin mixtures, cytoplasmic extracts and permeabilized yeast cells. Polymerization of actin waspromoted using phalloidin or inhibited using cytochalasin D or latrunculin.The polymeric filamentous F-actin, but not the monomeric globularG-actin, stabilized both the interaction of isolated glycolytic pathwayenzyme mixtures and the whole fermentation pathway, leading to higherfermentation activity. The associated complexes were resistant against inhibition as a result of viscosity (promoted by the disaccharide trehalose) orinactivation (using specific enzyme antibodies). In S. cerevisiae, a glycolyticmetabolon appear to assemble in association with F-actin. In this complex,fermentation activity is enhanced and enzymes are partially protectedagainst inhibition by trehalose or by antibodies.