Presence of connectin-like protein in white blood cells and platelets.

Connectin is known to be an anchoring protein of actomyosin filaments in skeletal muscle. Attempts were made to extract this protein from white blood cells and platelets in order to investigate its properties. The purified connectin-like protein obtained had a rubbery appearance and was insoluble in water and immobile on SDS gel-electrophoresis. Amino acid composition and electron microscopic features of the protein were similar to those of skeletal muscles. FITC-labeled antibody to the protein showed a positive reaction to the membrane fractions of red cells, white cells and platelets. In moving cells fluorescence was observed not only in pseudopod, but also in whole cytoplasm. No changes in the fluorescence patterns were observed with respect to moving stages or cell types. The presence of the protein beneath the cell membrane was also confirmed electron micrographically.