Fig. 3.
Structures of SDF12 dimers bound to the N-terminal domain of CXCR4. (A) N-terminal peptides corresponding to the first 38 amino acids of CXCR4 are illustrated. The sequence for p38 is identical to that of CXCR4 except for a Gly-Ser dipeptide on the N-terminus, which results from a cloning artifact, and a Cys28 → Ala28 mutation to prevent oxidative peptide dimer formation. The sulfated peptides are identical to p38 except for the inclusion of sulfotyrosine at position 21 for p38-sY1 and at 7, 12, and 21 for p38-sY3. (B) Representative intermolecular NOEs for the SDF12:p38-sY1 complex. Strips from 3D F1-13C-fliltered/F3-13C-edited NOESY-HSQC spectra acquired from a complex containing [U-15N,13C]-SDF12 and unlabeled p38-sY1 (left) and a complex containing [U-15N,13C]-p38-sY1 and unlabeled SDF12 (right) contain equivalent NOEs between the methyl group of Val18 of SDF12 and sTyr21 1Hδ of p38-sY1. Ensembles of the 20 lowest energy conformers for the SDF12:p38 (C), SDF12:p38-sY1 (D), and SDF12:p38-sY3 (E) complexes. SDF12 is shown in gray and the CXCR4 N-termini are orange. Sulfotyrosine residues in N-termini of CXCR4 are shown in red.