title: Structure of a plant β-galactosidase C-terminal domain.
abstract: Most plant β-galactosidases, which belong to glycoside hydrolase family 35, have a C-terminal domain homologous to animal galactose and rhamnose-binding lectins. To investigate the structure and function of this domain, the C-terminal domain of the rice (Oryza sativa L.) β-galactosidase 1 (OsBGal1 Cter) was expressed in Escherichia coli and purified to homogeneity. The free OsBGal1 Cter is monomeric with a native molecular weight of 15kDa. NMR spectroscopy indicated that OsBGal1 Cter comprises five β-strands and one α-helix. The structure of this domain is similar to lectin domains from animals, but loops A and C of OsBGal1 Cter are longer than the corresponding loops from related animal lectins with known structures. In addition, loop A of OsBGal1 Cter was not well defined, suggesting it is flexible. Although OsBGal1 Cter was predicted to be a galactose/rhamnose-binding domain, binding with rhamnose, galactose, glucose, β-1,4-d-galactobiose and raffinose could not be observed in NMR experiments.
authors.affiliation: School of Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
authors.forename: Thipwarin
authors.initials: T
authors.lastname: Rimlumduan
authors.affiliation: Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; Center for Scientific and Technological Equipment, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Hua
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan. Electronic address: ttanaka@tara.tsukuba.ac.jp.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: School of Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; Laboratory of Biochemistry, Chulabhorn Research Institute, Bangkok 10210, Thailand. Electronic address: cairns@sut.ac.th.
authors.forename: James R
authors.initials: JR
authors.lastname: Ketudat Cairns
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism; D005690:Galactose / Q000737:chemistry; D005696:Galactosidases / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D037102:Lectins / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008970:Molecular Weight; D012275:Oryza / Q000378:metabolism*; D000072756:Protein Conformation, alpha-Helical; D000072417:Protein Domains; D012210:Rhamnose / Q000737:chemistry; D016415:Sequence Alignment; D001616:beta-Galactosidase / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D037102:Lectins; D005696:Galactosidases; D001616:beta-Galactosidase; D005947:Glucose; D012210:Rhamnose; D005690:Galactose
keywords: C-terminal domain; NMR; Rice; Solution structure; β-galactosidase