Fig. 2.

Arginine anchoring sites for arginines of loops K1 L9 (R1109), K2 L8 (R1280) and K3 L10 (R1557). Salt bridge hydrogen bonding interactions with a conserved aspartic acid residue (D1139, D1319 and K1588 in K1, K2 and K3, respectively) are shown as dashed lines. A: Guanidinium ion (green) mediating an interaction between one K1 molecule (light blue) and two other crystallographic symmetrically related K1 molecules, coloured black(*) and orange(**), respectively (inset: detailed view of guanidinium ion-mediated reaction). B: Superimposition of arginine anchors and their anchoring sites in K1 (light blue), K2 (light green) and K3 (pink). Met1140, Asn991 and guanidinium ion of K1 are excluded. The positions of the K2 and K3 arginine atoms overlay with K1 R1109 with an rmsd of 1.0 Å and 1.3 Å, respectively