- SUR1 (CSG1/BCL21), a gene necessary for growth of Saccharomyces cerevisiae in the presence of high Ca2+ concentrations at 37 degrees C, is required for mannosylation of inositolphosphorylceramide. Beeler, T.J., Fu, D., Rivera, J., Monaghan, E., Gable, K., Dunn, T.M. Mol. Gen. Genet. (1997)