Purification and some properties of a new Ca2+-binding protein (TCBP-10) present in tetrahymena cilium.
A new Ca2+-binding protein, different from calmodulin, has been detected in the cilium and cell body of Tetrahymena. This protein, designated as TCBP-10, has been purified from the cells to homogeneity. TCBP-10 is an acidic protein (pI = 4.5) which shows a Ca2+-dependent mobility shift in alkali-glycerol-polyacrylamide gel electrophoresis. The protein is resistant to heat and trichloroacetic acid. The molecular weight of the protein is 10,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 22,000 by Sephadex G-50 gel filtration, suggesting that the native form of the protein is a dimer. The protein has a molar extinction coefficient of 6,500 at 282 nm. Equilibrium dialysis experiments revealed that the protein binds 1 mol of Ca2+/mol of protein with a dissociation constant of 27 microM. The protein contains a relatively large quantity of acidic amino acids, single residues of cysteine, histidine, and tryptophan, and no methionine. These properties are similar to those of some low molecular weight Ca2+-binding proteins belonging to the calmodulin family. Thus, the cilium of Tetrahymena contains a second Ca2+-binding protein in addition to calmodulin. We consider that TCBP-10 and calmodulin may play important cooperative roles in the Ca2+-regulation of ciliary movement in Tetrahymena.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002923:Cilia / Q000378:metabolism*; D003488:Cyanogen Bromide; D046911:Macromolecular Substances; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D013768:Tetrahymena / Q000378:metabolism*
D000596:Amino Acids; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D046911:Macromolecular Substances; D010446:Peptide Fragments; D003488:Cyanogen Bromide; D002118:Calcium