title: Tandem repeat of a seven-bladed beta-propeller domain in oligoxyloglucan reducing-end-specific cellobiohydrolase.
abstract: Oligoxyloglucan reducing-end-specific cellobiohydrolase (OXG-RCBH; EC 3.2.1.150) is an exoglucanase that recognizes the reducing end of oligoxyloglucan and releases two glucosyl residue segments from the main chain. The X-ray crystal structure of OXG-RCBH determined at 2.2 A resolution reveals a unique feature of this enzyme; OXG-RCBH consists of a tandem repeat of two similar domains, which are both folded into seven-bladed beta-propeller structures. The sequence alignment of the propeller blades, based on the structure, indicates that a weak repeat of the amino acid sequence occurred seven times to construct each domain. There is a cleft that can accommodate the substrate oligosaccharide between the two domains, which is a putative substrate binding subsite. Mutation of either Asp35 or Asp465, located in the putative catalytic center, to Asn resulted in a protein with no detectable catalytic activity, indicating the critical role of these amino acids in catalysis.
authors.affiliation: Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
authors.forename: Katsuro
authors.initials: K
authors.lastname: Yaoi
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Kondo
authors.forename: Natsuko
authors.initials: N
authors.lastname: Noro
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Sakae
authors.initials: S
authors.lastname: Tsuda
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Mitsuishi
mesh_terms: D000595:Amino Acid Sequence; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020080:Tandem Repeat Sequences
chemical_list: D043366:Cellulose 1,4-beta-Cellobiosidase