TRANSPORT OF CATIONIC AMINO-ACIDS BY THE MOUSE ECOTROPIC RETROVIRUS RECEPTOR

SUSCEPTIBILITY of rodent cells to infection by ecotropic murine leukaemia viruses (MuLV) is determined by binding of the virus envelope to a membrane receptor that has multiple membrane-spanning domains 1. Cells infected by ecotropic MuLV synthesize envelope protein, gp70, which binds to this receptor, thereby preventing additional infections. The consequences of envelope-MuLV receptor binding for the infected host cell have not been directly determined, partly because the cellular function of the MuLV receptor protein is unknown. Here we report a coincidence in the positions of the first eight putative membrane-spanning domains found in the virus receptor 1 and in two related proteins 2, the arginine 2-4 and histidine 2,3,5 permeases of Saccharomyces cerevisiae (Fig. 1), but not in any other proteins identified by computer-based sequence comparison of the GenBank data base 1. Xenopus oocytes injected with receptor-encoding messenger RNA show increased uptake of L-arginine, L-lysine and L-ornithine. The transport properties and the expression pattern of the virus receptor behave in ways previously attributed to y+ (refs 6, 7), the principal transporter of cationic L-amino acids in mammalian cells.