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. Author manuscript; available in PMC: 2009 Apr 20.
Published in final edited form as: J Mol Biol. 2006 May 11;359(5):1400–1409. doi: 10.1016/j.jmb.2006.04.052

Figure 5.

Figure 5

Identifcation of a CXCR4 sulfotyrosine 21 binding site on SDF-1α. Comparisons of 13C-1H HSQC spectra of SDF-1α in 20 mM MES pH 6.8 in the absence (black) or presence of 2 equivalents of P38 (green) or sY21 P38 (red). (a) Neither the H17 nor H25 Hε1-Cε1 signals show significant sulfation-dependent changes in chemical shift. (b) Among the methyl groups shown, only V49 is noticeably different in the presence of sY21 P38 (red) relative to the P38 complex (green). (c) Positively charged R47 from SDF-1α interacts with sY21 from CXCR4. Residues with sulfation-dependent shift perturbations >0.25 ppm (Figure 4(b)) are highlighted in orange as in Figure 4(c). Sidechains surrounding R41, including H25, N46 and Q48, are unaffected by sulfation (cyan). A sidechain methyl group of V49 (magenta sphere) adjacent to R47 is sensitive to sulfation of Y21 (shown in panel b).