ON STRUCTURAL PROTEIN OF FLAGELLAR OUTER FIBERS

Outer fibers have been isolated from sea urchin sperm flagella by a process of selective solubilization. The outer fibers, like most other microtubules reported in the literature, are composed of 40 Å globular subunits arranged longitudinally. The fibers may be solubilized to a characteristic protein which accounts for at least 95% of the total protein of the outer fiber. A minimal 3 s subunit of 59,000 molecular weight is formed in either 8 m-urea or 5 m-guanidine hydro-chloride; a 5.4 s particle with a molecular weight of 130,000 is produced in 50 mm-Salyrgan. The amino acid composition of the outer fiber protein strongly resembles that obtained by others from Tetrahymena cilia, and both proteins show much similarity to muscle actin, plasmodial actin and mitotic apparatus protein. © 1968.