Transport of cationic amino acids by the mouse ecotropic retrovirus receptor

Abstract

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 domains¹. 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 receptor¹ and in two related proteins², 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 Gen Bank data base¹. 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.