Isolation and characterization of acid phosphatase mutants in Schizosaccharomycespombe

72 mutants defective in the activity of the cell surface glycoprotein acid phosphatase were isolated and characterized. The mutants map in one genetic locus, phol. Many of them exhibit altered cell morphology. This characteristic cosegregates with acid phosphatase deficiency, implying that phol controls the activity of acid phosphatase and concomitantly cell morphology. Phol probably also influences growth rate and agglutination behaviour. By purifying acid phosphatase, two structurally related forms can be detected. One is inactive (form I) and one is the active acid phosphatase (form II). Mutant phol-270 and phol-277 lack the inactive form I. Mutant phol -38 exhibits mainly form I, form II being present only in minor amounts. Two other mutants examined differ only slightly from wildtype in their pattern of active and inactive forms. Tryptic peptide maps of the inactive and active acid phosphatase of the wildtype and the corresponding proteins of mutant phol-304 reveal similar structural alterations for the two mutant proteins. The results show that phol controls the expression of the active and inactive acid phosphatase. We conclude that phol represents the structural gene of the two forms of acid phosphatase.