Comparative analysis of the Bgs proteins family from Schizosaccharomyces pombe

The cell wall is a vital structure that confers mechanical strength and support to the fungal cell and represents a specific target for the development of new antifungal agents. S. pombe contains four Bgs (beta glucan synthesis) proteins that share a high identity and are putative catalytic subunits of the (1,3)β-D-glucan synthase (GS) activity. The bgs1⁺ mutants cps1-12, cps1-N12 and cps1-191 present septation and polarity defects. bgs4⁺ mutants cwg1-1 and cwg1-2 display a thermosensitive lethal phenotype and a dramatic GS decrease, orb11-59 is defective in cell polarity and pbr1-1, -2, -3, -6 and -8 are resistant to GS-specific antifungal drugs. In order to analyze whether each mutant phenotype is specific of the corresponding protein, we have performed a comparative analysis of Bgs1p, Bgs3p and Bgs4p. We located the mutations responsible for the bgs1 and bgs4 mutant phenotypes and created the corresponding mutation in bgs1⁺, bgs3⁺ and bgs4⁺ sequences. We included Papulacandin or Echinocandin resistance mutations described in the Saccharomyces cerevisiae homologous proteins Fks1p and Fks2p. The mutants have been tested for a series of phenotypes and we show that although the analyzed aminoacids are identical or well conserved, each mutation produces different phenotypes, conferring even lethality or no effect depending on the protein.