Fig 3.

(A) Ribbon diagram of subtilisin/CI2 complex structure. Subtilisin is shown in red, the N-terminal section of CI2 is shown in dark blue, and the C-terminal section of CI2 is shown in light blue. The reactive site peptide bond is at the junction of the dark and light blue segments. (B) Closer view of reactive site loop. CI2 side chains (labeled in white) and hydrogen bonds (yellow dotted lines) proposed to stabilize the positioning of the light blue (leaving group) side of the loop after acyl–enzyme formation (see text) are shown in detail. The serine, histidine, and aspartate of the subtilisin catalytic triad are also shown (labeled in yellow).