title: From structure to function: YrbI from Haemophilus influenzae (HI1679) is a phosphatase.
abstract: The crystal structure of the YrbI protein from Haemophilus influenzae (HI1679) was determined at a 1.67-A resolution. The function of the protein had not been assigned previously, and it is annotated as hypothetical in sequence databases. The protein exhibits the alpha/beta-hydrolase fold (also termed the Rossmann fold) and resembles most closely the fold of the L-2-haloacid dehalogenase (HAD) superfamily. Following this observation, a detailed sequence analysis revealed remote homology to two members of the HAD superfamily, the P-domain of Ca(2+) ATPase and phosphoserine phosphatase. The 19-kDa chains of HI1679 form a tetramer both in solution and in the crystalline form. The four monomers are arranged in a ring such that four beta-hairpin loops, each inserted after the first beta-strand of the core alpha/beta-fold, form an eight-stranded barrel at the center of the assembly. Four active sites are located at the subunit interfaces. Each active site is occupied by a cobalt ion, a metal used for crystallization. The cobalt is octahedrally coordinated to two aspartate side-chains, a backbone oxygen, and three solvent molecules, indicating that the physiological metal may be magnesium. HI1679 hydrolyzes a number of phosphates, including 6-phosphogluconate and phosphotyrosine, suggesting that it functions as a phosphatase in vivo. The physiological substrate is yet to be identified; however the location of the gene on the yrb operon suggests involvement in sugar metabolism.
authors.affiliation: Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, Maryland 20850, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Parsons
authors.forename: Kap
authors.initials: K
authors.lastname: Lim
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Tempczyk
authors.forename: Wojiech
authors.initials: W
authors.lastname: Krajewski
authors.forename: Edward
authors.initials: E
authors.lastname: Eisenstein
authors.forename: Osnat
authors.initials: O
authors.lastname: Herzberg
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins; D006193:Haemophilus influenzae / Q000201:enzymology*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009876:Operon; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C102536:KpsF protein, E coli; D021122:Protein Subunits; C073627:srlQ protein, E coli; D010744:Phosphoric Monoester Hydrolases