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Figure 5.
Figure 5. (a) Ribbon representation showing the orientation of the intermediate helix (blue) in wild-type rat trypsin;
colour coding and orientation as in Figure 1. ( p ) Indicates the cystine C168-C182, which is in a right-handed helical
conformation. Only side-chains of selected residues are shown for clarity. (b) In X(99/175/190)rT --(3) (yellow), the
helix is tilted by ca 208, with unwinding of the final turn. Cystine C168-C182 ( p ) isomerises to an extended fully
trans form, while F174 becomes buried in the body of the enzyme. (c) Stereo overlay of X(99/175/190)rT -- (3) and wild-
type rat trypsin, showing the cavity formed by the disulphide and the side-chains of I176, W215, P225 and V227. The
aromatic side-chain of F174 in X(99/175/190)rT -- (3) superimposes with that of trypsin Y172.
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