| Type: | Domain | Name: | N-(5'phosphoribosyl) anthranilate isomerase (PRAI) |
| Description: | N-(5'-phosphoribosyl) anthranilate isomerase (PRAI) is an enzyme that catalyses the third step of tryptophan biosynthesis. Proteins containing this domain include N-(5'-phosphoribosyl) anthranilate isomerase, anthranilate synthase component 2 and the tryptophan biosynthesis protein TRP1. Phosphoribosylanthranilate isomerase is monomeric and labile in most mesophilic microorganisms, but dimeric and stable in the hyperthermophile Thermotoga maritima(tPRAI) []. The comparison to the known 2.0 A structure of PRAI from Escherichia coli(ePRAI) shows that tPRAI has the complete TIM- or (beta alp ha)8-barrel fold, whereas helix alpha5 in ePRAI is replaced by a loop. The subunits of tPRAI associate via the N-terminal faces of their central beta-barrels. Two long, symmetry-related loops that protrude reciprocally into cavities of the other subunit provide for multiple hydrophobic interactions. Moreover, the side chains of the N-terminal methionines and the C-terminal leucines of both subunits are immobilized in a hydrophobic cluster, and the number of salt bridges is increased in tPRAI. These features appear to be mainly responsible for the high thermostability of tPRAI []. | Short Name: | PRAI |
