The seventh transmembrane domain of CC chemokine receptor 5 is critical for MIP-1 beta binding and receptor activation: Role of Met 287

CC chemokine receptor 5 (CCR5) is a high-affinity receptor for macrophage i nflammatory protein (MIP)-1 beta and functions as the major coreceptor for entry of macrophage-tropic (M-tropic) human immunodeficiency virus type 1 ( HIV-1). To evaluate the role of transmembrane domains (TM) in the receptor function of CCR5, the seventh transmembrane domain (TM7) was examined in a series of chimeric receptor constructs including CCR5TM (CCR5 backbone/CCR5 TM7 replaced with CCR1 TM7) and mutants of CCR5TM. The CCR5TM chimera exhi bited a dramatic reduction in receptor activation, as well as little or no MIP-1 beta binding. Further mutational analysis revealed that Met 287 in TM 7 of CCR5 is a critical molecular determinant for both MIP-1 beta binding a nd receptor activation. interestingly, all of the chimeric/mutated receptor s were biologically active in an HIV-1 coreceptor fusion assay, demonstrati ng that chemokine binding is independent of HIV-1 coreceptor activity. (C) 2001 Academic Press.