THE STRUCTURAL GENE FOR -MANNOSIDASE-1 IN DICTYOSTELIUM DISCOIDEUM

S. J. Free ¹, R. T. Schimke ¹, and W. F. Loomis ²

¹ Department of Biological Sciences, Stanford University, Stanford, California 94305
² Department of Biology, University of California at San Diego, La Jolla, California 92038

We have isolated 4 independent mutations affecting -mannosidase-1, a a developmentally regulated activity in Dictyostelium discoideum. Three of these result in a thermolabile -mannosidase-1 activity. One mutation also affects the substrate affinity (Km) of the activity. In diploids these mutations show a gene dosage effect and are all alleles. The structural gene for -mannosidase-1, as defined by these mutations, defines a new linkage group, linkage group VI. -Mannosidase-1 is probably a homopolymer with subunits of 54,000 daltons.

We have also mapped two temperature-sensitive-for-growth mutations onto two previously defined linkage groups.