Systematic Comparison of Cell Wall-Related Proteins of Different Yeasts

Vladimir Mrša,Bojan Žunar,Ksenija Lopandić,Renata Teparić,Dora Hrestak,Mateja Lozančić

doi:10.3390/jof7020128

Abstract

Yeast cell walls have two major roles, to preserve physical integrity of the cell, and to ensure communication with surrounding molecules and cells. While the first function requires evolutionary conserved polysaccharide network synthesis, the second needs to be flexible and provide adaptability to different habitats and lifestyles. In this study, the comparative in silico analysis of proteins required for cell wall biosynthesis and functions containing 187 proteins of 92 different yeasts was performed in order to assess which proteins were broadly conserved among yeasts and which were more species specific. Proteins were divided into several groups according to their role and localization. As expected, many Saccharomyces cerevisiae proteins involved in protein glycosylation, glycosylphosphatidylinositol (GPI) synthesis and the synthesis of wall polysaccharides had orthologues in most other yeasts. Similarly, a group of GPI anchored proteins involved in cell wall biosynthesis (Gas proteins and Dfg5p/Dcw1p) and other non-GPI anchored cell wall proteins involved in the wall synthesis and remodeling were highly conserved. However, GPI anchored proteins involved in flocculation, aggregation, cell separation, and those of still unknown functions were not highly conserved. The proteins localized in the cell walls of various yeast species were also analyzed by protein biotinylation and blotting. Pronounced differences were found both in the patterns, as well as in the overall amounts of different groups of proteins. The amount of GPI-anchored proteins correlated with the mannan to glucan ratio of the wall. Changes of the wall proteome upon temperature shift to 42 °C were detected.

Highlights

As single cell organisms, microbial cells are confronted with changes in their habitats that include variations in osmolyte concentrations
In this work we have performed a much more extensive comparison of 187 proteins related to S. cerevisiae cell wall with proteomes of 92 different yeasts, 77 of which were rather closely related to S. cerevisiae, while 15 were genetically more distant to the comparator
Cell wall has to fulfill its primary biological role in providing osmotic stability to the cell. Since the latter is mainly insured by the inner glucan layer of the wall it can be expected that the enzymatic apparatus for the biosynthesis and remodeling of β-1,3, β-1,6-glucan, and chitin are generally conserved among different yeasts

Summary

Introduction

Microbial cells are confronted with changes in their habitats that include variations in osmolyte concentrations. Cells form external envelopes, cell walls, which are able to withstand differences in osmotic pressure between the inner space and the surrounding This role is accomplished by building a polysaccharide network with required physical and chemical properties. These changes require additional enzymes for the remodeling of the carbohydrate network, but it should be noted that the growth of the cell itself requires flexibility of the cell wall This flexibility is accomplished by an equilibrium of enzymatic activities of different glycosidases and transglycosidases that shifts towards building, or decomposition of the walls, depending on the temporary and spatial requirements [2,3,4,5,6,7]. For quite a lot of wall proteins, their physiological roles have not been clarified yet

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Conclusion