The localization of Ca2+‐ATPase and Ca2+ binding proteins in the flagellum of guinea pig sperm

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Abstract
Ferritin‐labeled antibody to calmodulin was localized in flagella of guinea pig sperm. Ferritin granules were present on the surface of the medial portion of the coarse fibers, and in the matrix immediately surrounding this segment of the fibers. The results demonstrate that calmodulin is confined to regions close to the tubulin‐dynein systems os the axoneme. A calcium‐dependent ATPase was localized in the same region by trapping the reaction product with cadmium. The presence together of calmodulin and the Ca2+‐ATPase close to the axonemal complex suggests that they function to control the concentration of Ca2+, which in turn may regulate the action of the dynein ATPase, and sperm motility. The remainder of the coarse fiber surface also contains specialized material as evidenced by intense staining with ethanolic phosphotungstic acid. These data suggest that the role of the coarse fibers is complex and may not be solely structural.