Phosphorylation of a 70 kD Tetrahymena ciliary membrane protein is associated with ciliogenesis.

To identify proteins in Tetrahymena thermophila which were phosphorylated during ciliary assembly, the antiphosphoprotein antibody MPM-2 was used to probe blots of total ciliary protein or axonemal and ciliary membrane/matrix fractions from full-length cilia, regenerating cilia, or cilia that had grown to full-length following deciliation. A 70 kD protein was recognized by MPM-2 only in blots of total ciliary protein from regenerating cilia and of the membrane/matrix fraction from regenerating cilia. MPM-2 did not recognize this protein in blots of axonemal fractions of regenerating cilia or in blots of either axonemal or membrane/matrix fractions of full-length cilia. The results indicate that the 70 kD ciliary membrane protein was phosphorylated only in ciliary membranes or matrices of growing cilia. After the cilia reached full-length the membrane/matrix protein was either dephosphorylated or removed from the cilia. These observations support the hypothesis that the 70 kD membrane/matrix protein functions primarily during ciliary assembly.