Location of a Single β-Tubulin Gene Product in Both Cytoskeletal and Mitotic-spindle Microtubules in Physarum polycephalum

SUMMARY: In the mutant BEN210 of Physarum polycephalum several β-tubulins are detectable. β-tubulin is unique to the myxamoeba, β-tubulin is unique to the plasmodium, and the mutant β-210 tubulin encoded by the benD210 allele is present in both cell types. In order to analyse the subcellular distribution of the β-210 polypeptide, we prepared cytoskeletons from myxamoebae and mitotic spindles from plasmodia, and examined the tubulin polypeptide composition of these microtubular organelles by two-dimensional gel electrophoresis and immunoblotting. The results show that the β-210 tubulin is present in microtubules of both the cytoskeleton and the intranuclear mitotic spindle. Thus a single β-tubulin gene product can participate in multiple microtubular organelles in distinct cellular compartments.