Role of CD4 hinge region in GP120 utilization by immunoglobulin domain 1.
Immunoglobulin-like domain 1 of CD4 (D1-CD4) promotes HIV infection by binding the envelope glycoprotein (ENV) and exposing its coreceptor-binding site. To study CD4-ENV-coreceptor interactions, we characterized hybrid receptors having domains 1 and 2 of CD4 (D1D2-CD4) joined to the N-terminus of chemokine receptors CCR5, CXCR4, CXCR2, and DARC. Hybrid receptors showed conserved ENV-coreceptor specificity in cell-cell fusion assays. Although D1D2-CD4- CCR5 was sufficient to permit ENV-mediated fusion, D1-CD4- CCR5 and human D1/mouse D2-CD4- CCR5 lacked CD4 function and binding to a neutralizing antibody mapped to D1-CD4. Chimeric D1D2-CD4 joined to CCR5 revealed that the C-terminal 20 residues of human D2-CD4 are required for efficient ENV-mediated fusion. Mutagenesis of hybrid receptors showed the importance of residues forming D1- D2 CD4 interdomain contacts and hinge region proximal residues. Mutagenesis of WT human CD4 confirmed that residues forming D1- D2 interdomain contacts and hinge-region proximal residues contribute positively to CD4 activity in the full-length receptor.[1]References
- Role of CD4 hinge region in GP120 utilization by immunoglobulin domain 1. Murray, J.L., Hu, Q.X., Navenot, J.M., Peiper, S.C. Biochem. Biophys. Res. Commun. (2002) [Pubmed]
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