Figure 3.

Mapping of Ile-methyl-NOE clusters onto the X-ray structure of ERK2. (a) Strip plots of the 3D (¹³C, ¹³C, ¹H) HMQC-NOESY-HMQC spectra for 0P-ERK2 illustrating the Ile-methyl-NOE clusters in the protein. Diagonal peaks are marked with squares, the horizontal solid lines indicate NOE cross peaks to other methyls, and dashed lines indicate where a cross peak is not observed. Asterisks mark peaks that arise from bleed-through in the third dimension from a different methyl resonance, and double asterisks indicate noise peaks or artifacts. The numbers at the bottom of each strip plot are the ¹³C chemical shift for this methyl plane. (b) Geometry models illustrating the various Ile-methyl-NOE clusters in ERK2. The numbers at the vertex represent the methyl for that strip plot in (a) and a line connecting two vertices indicates an observed NOE between these two methyls with single and double headed arrows indicating that one and two NOE cross peaks, respectively, were observed between the two resonances. (c) Ile-methyl clusters in the X-ray structure of ERK2 that fit the geometry models in (b). The upper panel shows the only six-residue Ile-methyl cluster (using an 8 Å cutoff), the middle panel shows the only three-residue Ile-methyl cluster, and the bottom two panels show two of the five 2-residue Ile-methyl clusters. Ile side chains are shown as red lines, their C^δ1 methyls as red spheres and the backbone is a gray ribbon.