Immunofluorescent subcellular localization of some muscle proteins: a comparison between tissue sections and isolated myofibrils.

The localization of parvalbumin in fish white muscle and of the calcium binding protein, of arginine kinase and of glycogen phosphorylase in crayfish tail muscle have been investigated by immunofluorescence using isolated myofibrils and muscle sections as starting materials. It is shown that the four proteins appear to be localized on the thin filaments when myofibrils are used as starting material. This result contrasts with previous observations where it appeared that parvalbumin in fish muscle and arginine kinase in crayfish muscle were distributed uniformly within the cell. This discrepancy is discussed in relation to the high solubility of these proteins. In the light of the present knowledge about striated muscles from these two organisms, it seems that the roles of parvalbumin in fish and of the calcium binding protein in crayfish are probably different.