Relation between actin-associated proteins and membrane immunoglobulin in B-cells.

The myosin-affinity technique, along with conventional immunoaffinity chromatography of membrane immunoglobulin (mIg), was used to study the relation between proteins that bind to actin, and those that co-isolate with the mIg of normal chicken B-cells. In the case of biosynthetically-labeled cells, we found approximately 13 actin-associated polypeptides. Of this group, eight could be labeled with 125I surface labeling. When the actin-associated proteins were compared to proteins that co-isolate with mIg during immunoaffinity chromatography, we found that two of them (mol. wts 55,000 and 34,000) co-isolate with mIg. The 55,000 mol. wt polypeptide can be labeled with 125I surface labeling techniques, while the 34,000 mol. wt protein cannot, suggesting that only the 55,000 mol. wt protein is exposed on the outer surface of the plasma membrane. It is speculated that the function of these proteins may be involved in linking mIg to actin and perhaps to the cytoskeleton.