The stress response protein Hsp12p increases the flexibility of the yeast Saccharomyces cerevisiae cell wall.

The yeast S. cerevisiae cell wall comprising a 10 nm thick layer of polysaccharides, predominantly beta(1,3)-glucan and proteins, is the interface between the cell and the neighbouring environment. As such it is not a static entity but rather one that is dynamically remodelled in response to changes in the environmental conditions. We have recently proposed from studies using yeast cells lacking the gene encoding Hsp12p (Deltahsp12 yeast) and from incorporation of Hsp12p into agarose, used as a model system for the beta-glucan layer of the cell wall, that the hydrophilic stress response cell wall protein Hsp12p acts as a cell wall plasticizer. In this report we have used force spectroscopy to confirm that Deltahsp12 yeast are indeed less flexible than the wild type strain. The spring constant of the cell wall of Deltahsp12 yeast, kcw was determined to be 72+/-3 mN m-1 as compared to 17+/-5 mN m-1 obtained for the wild type strain. A similar result was found on the basis of a quantitative analysis of the electrophoretic mobilities measured for the two yeast strains. Those indicated that the hydrodynamic permeability quantified through the softness parameter of the external layer of Deltahsp12 cells was smaller than the one of wild type cells. We proposed from surface infrared spectroscopy measurements that yeast compensate for the lack of Hsp12p by reducing the carbohydrate/proteins ratio of the cell wall or increasing the cell wall chitin content.