Allovalency observed by transferred NOE: interactions of sulfated tyrosine residues in the N-terminal segment of CCR5 with the CCL5 chemokine.

The N-terminal segment of the chemokine receptor Human CC chemokine receptor 5 (CCR5), Nt-CCR5, contains four tyrosine residues, Y3, Y10, Y14, and Y15. Sulfation of at least two of these tyrosine residues was found to be essential for high-affinity binding of CCR5 to its chemokine ligands. Here, we show that among the monosulfated Nt-CCR5(8-20) peptide surrogates (sNt-CCR5) those sulfated at Y15 and Y14 have the highest affinity for the CC chemokine ligand 5 (CCL5) chemokine in comparison with monosulfation at position Y10. Sulfation at Y3 was not investigated. A peptide sulfated at both Y14 and Y15 has the highest affinity for CCL5 by up to a factor of 3, in comparison with the other disulfated (sNt-CCR5) peptides. Chemical shift perturbation analysis and transferred nuclear Overhauser effect measurements indicate that the sulfated tyrosine residues interact with the same CCL5-binding pocket and that each of the sulfated tyrosines at positions 10, 14, and 15 can occupy individually the binding site on CCL5 in a similar manner, although with somewhat different affinity, suggesting the possibility of allovalency in sulfated Nt-CCR5 peptides. The affinity of the disulfated peptides to CCL5 could be increased by this allovalency and by stronger electrostatic interactions.