THE STRUCTURAL GENE FOR α-MANNOSIDASE-1 IN DICTYOSTELIUM DISCOIDEUM

We have isolated 4 independent mutations affecting α-mannosidase-1, a a developmentally regulated activity in Dictyostelium discoideum. Three of these result in a thermolabile α-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 α-mannosidase-1, as defined by these mutations, defines a new linkage group, linkage group VI. α-Mannosidase-1 is probably a homopolymer with subunits of 54,000 daltons.