Figure 3.

The dimer interface. This view focuses on interactions that influence dimer formation. (A) Stereoview as in Fig. 2A showing the side chains of Phe-390 and Tyr-331 and the catalytic Cys-285 in the active (Left) and inactive (Right) catalytic domains, within the dimeric structure. (B) Stereoview of a superposition of the inactive monomer (gray) onto the active one (red). Rotation of Phe-390 about C^α–C^β occurs in the transition from the inactive to the active conformation, allowing a compensatory rotation of Tyr-331 around its C^α–C^β. This in turn may help to promote the catalytic conformation of Cys-285. The yellow side-chain represents the position of Phe-390′ in a hypothetical dimer made from two active catalytic domains. Note that it would clash with the active conformation of Phe-390, eliminating the possibility of having two active monomers in this dimer.