S-modulin-like proteins in the retina.

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In the frog retina, we previously purified an S-modulin-like protein, s26. In the present project, we examined (1) the aminoacid sequence, (2) the tissue localization and (3) the function of s26. In addition, the possible function of S-modulin-like proteins found in other tissues are studied.(1) The amino acid sequence of s26 is 66% identical to S-modulin. Surprisingly, s26 shows 77% identity, a higher homology to visinin, a cone specific calcium-biding protein in chick retina.(2) The antibody raised to a peptide specific to s26 stained a photoreceptor layr of the frog retina.The exact location of the positive signal in the layr is now in progress.(3) The function of s26 seems to be the same as that of S-modulin. This conclusion was drawn from the finding that s26 inhibited rhodopsin phosphorylation at high calcium concentrations as S-modulin does.(4) Many S-modulin-like proteins have been found in brain, but their functions are titally unknown. We examined 7 of these proteins and found that all of the 7 proteins tested showed a similar effect as S-modulin.This finding strongly suggests that these proteins function as a calciumdependent regulator of a phoshorylation reaction.