Paramagnetic relaxation effects observed for 1
N HSQC correlations of Ca2+
-S100A4 in a titration with a MIIA1893-1923
peptide spin-labeled at its C-terminus. (A) 1H-15N HSQC correlations for Glu23, Asp51, and Lys100 of Ca2+-bound S100A4 in the presence of increasing amounts of spin-labeled MIIA1893-1923 peptide (0, 2.6, 5.3, 11, 21, 42, and 95 μM). (B) Ribbon diagram of Ca2+-bound S100A4 (PDB 2Q91) with residues affected by the spin label highlighted in blue. Residues exhibiting the strongest effects are shown as spheres. Arg99 and Lys100 are not shown on the ribbon diagram since these residues are not observed in the X-ray structure due to the mobility of the C-terminal loop .