Properties of the protein subunit of central-pair and outer-doublet microtubules of sea urchin flagella.
The subunit protein has been isolated from the central-pair and outer-doublet microtubules of sea urchin sperm tails. Both proteins have a sedimentation constant of 6S and a molecular weight of 120,000. Both are converted to a 60,000 molecular weight species by denaturation in 6 M guanidine hydrochloride and reduction with mercaptoethanol. The reduced-alkylated proteins have the same R(f) on disc electrophoresis, and the same amino acid composition, which is very similar to that of muscle actin. The central-pair protein has one binding site for colchicine per 120,000 g. Both proteins appear to have a guanine nucleotide binding site, but the ability to bind GTP in solution has been demonstrated only for the central-pair protein. Although 1 mole of guanine nucleotide is bound per 60,000 g to outer-doublet tubules, the protein obtained by dissolving the doublets at pH 10.5 has lost the guanine nucleotide-binding site and also shows little or no colchicine-binding activity. Comparison of the properties of the isolated protein with electron microscopic evidence on structure of microtubules suggests that the chemical subunit (M = 120,000) consists of two of the 40 A morphological subunits.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002855:Chromatography, Thin Layer; D004447:Echinodermata / Q000032:analysis*; D004589:Electrophoresis, Disc; D005407:Flagella / Q000032:analysis*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009711:Nucleotides / Q000032:analysis; D009940:Organoids / Q000032:analysis*; D011506:Proteins / Q000032:analysis*; D014783:Viscosity
D000596:Amino Acids; D009711:Nucleotides; D011506:Proteins