title: Crystal structure of histidyl-tRNA synthetase from Escherichia coli complexed with histidyl-adenylate.
abstract: The crystal structure at 2.6 A of the histidyl-tRNA synthetase from Escherichia coli complexed with histidyl-adenylate has been determined. The enzyme is a homodimer with a molecular weight of 94 kDa and belongs to the class II of aminoacyl-tRNA synthetases (aaRS). The asymmetric unit is composed of two homodimers. Each monomer consists of two domains. The N-terminal catalytic core domain contains a six-stranded antiparallel beta-sheet sitting on two alpha-helices, which can be superposed with the catalytic domains of yeast AspRS, and GlyRS and SerRS from Thermus thermophilus with a root-mean-square difference on the C alpha atoms of 1.7-1.9 A. The active sites of all four monomers are occupied by histidyl-adenylate, which apparently forms during crystallization. The 100 residue C-terminal alpha/beta domain resembles half of a beta-barrel, and provides an independent domain oriented to contact the anticodon stem and part of the anticodon loop of tRNA(His). The modular domain organization of histidyl-tRNA synthetase reiterates a repeated theme in aaRS, and its structure should provide insight into the ability of certain aaRS to aminoacylate minihelices and other non-tRNA molecules.
authors.affiliation: INSERM/ULP BP 163, Illkirch, France.
authors.forename: J G
authors.initials: JG
authors.lastname: Arnez
authors.forename: D C
authors.initials: DC
authors.lastname: Harris
authors.forename: A
authors.initials: A
authors.lastname: Mitschler
authors.forename: B
authors.initials: B
authors.lastname: Rees
authors.forename: C S
authors.initials: CS
authors.lastname: Francklyn
authors.forename: D
authors.initials: D
authors.lastname: Moras
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray / Q000379:methods; D004926:Escherichia coli / Q000201:enzymology*; D006639:Histidine / Q000031:analogs & derivatives* / Q000378:metabolism; D006643:Histidine-tRNA Ligase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D011994:Recombinant Proteins; D006639:Histidine; D006643:Histidine-tRNA Ligase; D000241:Adenosine