Coelomocyte spectrin.

We have investigated the presence and localization of an alpha-spectrinlike protein and its potential role in the morphological transformation of sea urchin coelomocytes. In immunofluorescence images there is a diffuse fluorescence throughout the petaloid cytoplasm, indicating a random distribution of the spectrinlike protein prior to the transformation. As these cells from filopodia, there is a coincident appearance of a spectrinlike protein, as seen in fluorescent images, at the site of filopodial initiation. As the filopodia continue to form and lengthen, the spectrin localization parallels their development. There is a single polypeptide observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of whole coelomocyte lysates that cross-reacts with the anti-alpha-spectrin immunogen and comigrates with it at 240 kilodaltons.