Separation of inhibition and activation of the allosteric yeast chorismate mutase.

ABSTRACT: Yeast chorismate mutase (EC 5.4.99.5) shows homotropic activation by the substrate, allosteric activation by tryptophan, and allosteric inhibition by tyrosine. In this study mutants of chorismate mutase have been found that remain sensitive to one allosteric effector (tryptophan) but insensitive to the other (tyrosine). These mutations are located in the catalytic domain: loop 220s (212-226) and helix 12 (227-251). The first example starts with the Thr-266 --> Ile mutant that had previously been shown to be locked in the activated R state. The additional mutation Ile-225 --> Thr unlocks the R state and restores the activation by tryptophan but not the inhibition by tyrosine. The second example refers to a molecular trigger for the switch between the T and R state: a hydrogen-bonded system,

SUBMITTER: Schnappauf G 

PROVIDER: S-EPMC19661 | biostudies-literature | 1998 Mar

REPOSITORIES: biostudies-literature