TEMPORAL PHOSPHORYLATION OF THE DROSOPHILA PERIOD PROTEIN

The period gene (per) is required for Drosophila melanogaster to manif est circadian (similar or equal to 24 hr) rhythms. We report here that per protein (PER) undergoes daily oscillations in apparent molecular mass as well as abundance. The mobility changes are largely or exclusi vely due to multiple phosphorylation events. The temporal profile of t he classic short-period form of PER (PERS) is altered in a manner cons istent with the mutant strain's behavioral phenotype. As changes in ab undance and phosphorylation persist under constant environmental condi tions, they reflect or contribute to a free-running rhythm. We suggest that the phosphorylation status of PER is an important determinant in the Drosophila clock's time-keeping mechanism.