Photoaffinity labelling of the nucleoside transporter of cultured mouse lymphoma cells.

Nitrobenzylthioniosine (NBMPR), a potent and specific inhibitor of nucleoside transport, is bound reversibly by high affinity sites on nucleoside transporter proteins of erythrocyte membranes and, upon photoactivation, NBMPR molecules become covalently bonded to the sites. This study showed that [3H]NBMPR molecules reversibly bound to intact S49 and L5178Y mouse lymphoma cells became covalently bound upon exposure to UV light. Electrophoretic analysis of plasma membrane fractions from the labelled cells showed that 3H was present in polypeptides which migrated as a major band with an apparent Mr of 45000-65000.