Structural Insight into the Tetramerization of an Iterative Ketoreductase SiaM through Aromatic Residues in the Interfaces
Figure 6
The composition of the SiaM tetramer.
The SiaM tetramer is constructed through symmetry operations. (a) The square-shaped SiaM tetramer. Each protomer is colored in red, yellow, green and cyan separately. (b) The aromatic stacking interactions in the N-terminal interface. The Phe123, Tyr111 in one protomer and Phe123′, Tyr111′ in the other protomer are shown as sticks and colored in red. The rest of the protomers are colored in yellow and green separately. The aromatic residues form T-shaped aromatic stacking interactions. (c) The aromatic stacking interaction in the C-terminal interface. The Phe227, Tyr235 in one protomer and Phe227′, Tyr235′ in the other protomer are shown as sticks and colored in red. The rest of the protomers are colored in green and cyan separately. The Phe227 and Phe227′ form a parallel-displaced aromatic stacking interaction. (d) The interface formation around Tyr235. The Tyr235 residue is colored in red and shown as sticks. The rest of the molecule is shown in ribbon. The neighboring protomer is shown as surface. A deep cavity is clearly visible at the Tyr235 binding site. The residues in the cavity are shown as sticks.