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. 2012 Jun 7;287(32):26618–26629. doi: 10.1074/jbc.M112.381079

FIGURE 7.

FIGURE 7.

Molecular basis of a key residue critical for CP32M resistance. A, a portion of a ribbon model of the 6-HB structure formed by the NHR546–588/CP32M chimera. Residues that are important to CP32M resistance and the interaction with NHR helix are shown in stick model. Glu-648 and Lys-644 form an intrahelical salt bridge on CP32M, and Glu-648 forms another interhelical salt bridge with Arg-557 on the NHR helix. The salt bridges are indicated by a dashed line. B, model (generated by Coot and PyMOL) of the 6-HB structure formed by the NHR546–588/CP32M chimera with mutation N553D (equivalent to N42D). The assumed salt bridge between Asp-553 and Arg-557 (indicated by a red dashed line) will neutralize the positive charge of Arg-557, thus disrupting the interhelical salt bridge between Arg-557 and Glu-648 on CP32M and disfavoring the electrostatic interaction between CP32M and its NHR target. C, a portion of a ribbon model of the 6-HB structure formed by T21/CP621–652 peptide (Protein Data Bank ID 3VGX). The NHR helices are colored in gray, and CP621–652 peptide is colored in green. The corresponding residues shown in A and B are shown here in stick model with labels. The corresponding salt bridge between Arg-557 and Glu-648 (distance 4.8 Å) cannot be identified in this structure.