Two tricks in one bundle: helix-turn-helix gains enzymatic activity.

ABSTRACT: Many examples of enzymes that have lost their catalytic activity and perform other biological functions are known. The opposite situation is rare. A previously unnoticed structural similarity between the lambda integrase family (Int) proteins and the AraC family of transcriptional activators implies that the Int family evolved by duplication of an ancient DNA-binding homeodomain-like module, which acquired enzymatic activity. The two helix-turn-helix (HTH) motifs in Int proteins incorporate catalytic residues and participate in DNA binding. The active site of Int proteins, which include the type IB topoisomerases, is formed at the domain interface and the catalytic tyrosine residue is located in the second helix of the C-terminal HTH motif. Structural analysis of other 'tyrosine' DNA-break

SUBMITTER: Grishin NV 

PROVIDER: S-EPMC102627 | biostudies-literature | 2000 Jun

REPOSITORIES: biostudies-literature