Sulfopeptide probes of the CXCR4/CXCL12 interface reveal oligomer-specific contacts and chemokine allostery

摘要: Tyrosine sulfation is a post-translational modification that enhances protein-protein interactions and may identify druggable sites in the extracellular space. The G protein-coupled receptor CXCR4 prototypical example with three potential at positions 7, 12, 21. Each sulfotyrosine participates specific contacts its chemokine ligand structure of soluble, dimeric CXCL12:CXCR4(1-38) complex, but their relative importance for binding activation by monomeric remains undefined. NMR titrations short sulfopeptides showed tyrosine motifs varied widely contributions to CXCL12 affinity site specificity. Whereas Tyr21 sulfopeptide bound same as previously solved structures, Tyr7 Tyr12 interacted nonspecifically. Surprisingly, unsulfated peptide occupied hydrophobic on monomer inaccessible dimer. Functional analysis mutants validated individual modifications (Tyr21 > Tyr7) activation. Biophysical measurements also revealed cooperative relationship between dimerization, first allosteric behavior chemokine. Future ligands occupy sTyr21 recognition act both competitive inhibitors modulators function. Together, our data suggests does not ubiquitously enhance complex distinct patterns could encode oligomer selectivity, implying another layer regulation signaling.