Crystal structure of glycosyltrehalose trehalohydrolase from the hyperthermophilic archaeum Sulfolobus solfataricus.

摘要: The crystal structure of glycosyltrehalose trehalohydrolase from the hyperthermophilic archaeum Sulfolobus solfataricus KM1 has been solved by multiple isomorphous replacement. enzyme is an α-amylase (family 13) with unique exo-amylolytic activity for glycosyltrehalosides. It cleaves α-1,4 glycosidic bond adjacent to trehalose moiety release and maltooligo saccharide. Unlike most other family 13 glycosidases, does not require Ca2+ activity, it contains N-terminal extension ∼100 amino acid residues that homologous domains found in many glycosidases recognize branched oligosaccharides. Crystallography revealed exist as a homodimer covalently linked intermolecular disulfide at residue C298. existence was confirmed biochemical analysis mutagenesis. forms independent domain connected catalytic extended linker. functionally essential binding site B α-amylases be replaced hydrophobic packing interactions. also very unusual excursion (β/α)8 barrel domain. This originates bottom between helix 6 strand 7, but folds upward distorted α-hairpin form part substrate cleft wall possibly critical enzyme’s selectivity. Participation α-β loop formation novel feature observed known enzymes.