Crystal structure of Thermotoga maritima alpha-L-fucosidase. Insights into the catalytic mechanism and the molecular basis for fucosidosis.
Fucosylated glycoconjugates are involved in numerous biological events, and alpha-l-fucosidases, the enzymes responsible for their processing, are therefore of crucial importance. Deficiency in alpha-l-fucosidase activity is associated with fucosidosis, a lysosomal storage disorder characterized by rapid neurodegeneration, resulting in severe mental and motor deterioration. To gain insight into alpha-l-fucosidase function at the molecular level, we have determined the crystal structure of Thermotoga maritima alpha-l-fucosidase. This enzyme assembles as a hexamer and displays a two-domain fold, composed of a catalytic (beta/alpha)(8)-like domain and a C-terminal beta-sandwich domain. The structures of an enzyme-product complex and of a covalent glycosyl-enzyme intermediate, coupled with kinetic and mutagenesis studies, allowed us to identify the catalytic nucleophile, Asp(244), and the Brønsted acid/base, Glu(266). Because T. maritima alpha-l-fucosidase occupies a unique evolutionary position, being far more closely related to the mammalian enzymes than to any other prokaryotic homolog, a structural model of the human enzyme was built to document the structural consequences of the genetic mutations associated with fucosidosis.
Sulzenbacher
Gerlind
G
Architecture et Fonction des Macromolécules Biologiques, UMR 6098, CNRS, and Universités Aix-Marseille I and II, 31 Chemin J. Aiguier, F-13402 Marseille Cedex 20, France.
Bignon
Christophe
C
Nishimura
Takeshi
T
Tarling
Chris A
CA
Withers
Stephen G
SG
Henrissat
Bernard
B
Bourne
Yves
Y
D002384:Catalysis; D020134:Catalytic Domain; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005645:Fucosidosis / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010802:Phylogeny; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D020124:Thermotoga maritima / Q000201:enzymology*; D005644:alpha-L-Fucosidase / Q000737:chemistry*
D005644:alpha-L-Fucosidase