The cytomegalovirus US28 protein binds multiple CC chemokines with high affinity

Human cytomegalovirus encodes several proteins with high similarity to seven transmembrane domain receptors. We investigated the ability of one of these proteins, the product of the US28 open reading frame, to bind various chemoattractant ligands. When transfected into COS-7 cells, the US28 product conferred high affinity binding to the labeled chemokines monocyte chemoattractant protein-1 (MCP-1) (Kd = 6.0 x 10(-10) M) and RANTES (Kd = 2.7 x 10(-10) M). Binding of these labeled ligands could be competed by the unlabeled macrophage inflammatory proteins MIP-1 alpha and MIP-1 beta, with Kd values in the range 1.2 x 10(-9) to 7.5 x 10(-9) M. Comparisons of the sequences of US28 and other receptors that bind chemokines should help to define regions responsible for receptor-ligand interactions.