Ribosomal proteins of the dimorphic fungus, Mucor racemosus.

Ribosomal proteins of the dimorphic fungus Mucor racemosus were isolated and characterized by 2-dimensional gel electrophoresis. Proteins from ribosomes of the yeast and mycelial phase were compared, and were found to be qualitatively indistinguishable. The only consistent difference in the patterns of proteins was in a protein of the 40S subunit, S-6. This protein was phosphorylated in yeast and hyphae forms, but not in asexual sporangiospores. Studies on protein S-6 showed that it contained 3 phosphate residues per molecule of protein when maximally phosphorylated. In this form 3 different tryptic peptides were shown to contain a single phosphoserine. The S-6 protein also existed in forms containing 1 or 2 phosphates per molecule, depending on growth conditions.