The Identification of Actin as a Major Lymphocyte Component

Abstract

Lymphocytes derived from pig mesenteric lymph node and mouse spleen have been shown to contain a major protein component which a) co-migrates on one-dimensional SDS-PAGE with purified pig muscle actin, and b) possesses the same isoelectric point as muscle action on two-dimensional gel electrophoresis. Further, limited proteolytic digestion of the lymphocyte actin-comigrating band by S. aureus V8-protease revealed extensive primary sequence homology with purified muscle actin. Based on the virtual identity of molecular size, charge, and primary sequence, we conclude that the actin-comigrating band represents lymphocyte actin. The appearance of lymphocyte actin as a nonspecific “contaminant” of immune precipitates has also been discussed.