Some properties of the protein forming the outer fibers of cilia.
Cilia were isolated from Tetrahymena pyriformis by an ethanol-calcium procedure. Solutions of outer-fiber protein were obtained either by aqueous extraction of an acetone powder of whole cilia, or by dissolving the isolated outer-fibers in 0.6 M KCl. In aqueous solution, the outer-fiber protein has a sedimentation coefficient of 6.0S and a molecular weight of 104,000 +/- 14,000. In 5 M guanidine hydrochloride solution the molecular weight falls to 55,000 +/- 5,000. After reduction and alkylation in 8 M urea, about 95% of the protein migrates as a single band on electrophoresis in polyacrylamide gel at pH 8.9; the migration velocity is identical with that of reduced and alkylated actin. Freshly prepared outer-fiber protein contains about 7.5 sulfhydryl groups per 55,000 g of protein. The amino acid composition of outer-fiber protein resembles that of actin, with such differences as occur being of the same order as those between actins from different species of animal.
Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138.
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Renaud
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Rowe
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Gibbons