Composite Active Site of an ABC ATPase

Composite active site of an ABC ATPase: MutS uses ATP to verify mismatch recognition and authorize DNA repair.

The MutS protein initiates DNA mismatch repair by recognizing mispaired and unpaired bases embedded in duplex DNA and activating endo- and exonucleases to remove the mismatch. Members of the MutS family also possess a conserved ATPase activity that belongs to the ATP binding cassette (ABC) superfamily. Here we report the crystal structure of a ternary complex of MutS-DNA-ADP and assays of initi...

Composite active site of chondroitin lyase ABC accepting both epimers of uronic acid.

Enzymes have evolved as catalysts with high degrees of stereospecificity. When both enantiomers are biologically important, enzymes with two different folds usually catalyze reactions with the individual enantiomers. In rare cases a single enzyme can process both enantiomers efficiently, but no molecular basis for such catalysis has been established. The family of bacterial chondroitin lyases A...

Biochemical characterization of the chondroitinase ABC I active site.

cABC I (chondroitinase ABC I) from Proteus vulgaris is a GalAG (galactosaminoglycan) depolymerizing lyase that cleaves its substrates at the glycosidic bond via beta-elimination. cABC I cleaves a particularly broad range of GalAG substrates, including CS (chondroitin sulphate), DS (dermatan sulphate) and hyaluronic acid. We recently cloned and recombinantly expressed cABC I in Escherichia coli,...

Degenerate ABC composite site is stably glued together by trapped ATP

An article published in this issue (see Tsai et al.) provides important advances in our understanding of the gating mechanism of the CFTR, the chloride channel mutated in cystic fibrosis patients. Indeed, the relevance of the conclusions goes beyond understanding CFTR, extending at least to the subfamily of ABC proteins to which CFTR belongs, and perhaps also to the entire superfamily. ABC prot...

PROBING THE ACTIVE SITE OF RHODANESE WITH DISULFIDE REAGENTS