Identification of receptors for prothymosin alpha on human lymphocytes

alpha Prothymosin a (ProT alpha) is a highly conserved and widely distribut ed protein whose physiological functions remain elusive. In previous work w e identified high and low affinity-binding sites for ProT alpha in lymphoid cells. Here we demonstrate, by affinity crosslinking and affinity chromato graphy, the existence of three binding partners (31,29, and 19 kDa) for Pro T alpha in the membrane of PHA-activated lymphoblasts. These surface molecu les possess the expected affinity and specificity for a ProT alpha receptor . Examination of the expression of this complex of molecules by flow cytome try reveals that they bind ProT alpha in a specific and saturable way. In a ddition, the distribution of the receptor on the cell surface was studied b y fluorescence microscopy; a cap-like structure at one of the poles of the cells was identified. These results represent a new and promising approach in the research on ProT alpha, opening the way toward the understanding of the molecular mechanism of action of this protein.