title: An enzyme captured in two conformational states: crystal structure of S-adenosyl-L-homocysteine hydrolase from Bradyrhizobium elkanii.
abstract: S-Adenosyl-L-homocysteine hydrolase (SAHase) is involved in the enzymatic regulation of S-adenosyl-L-methionine (SAM)-dependent methylation reactions. After methyl-group transfer from SAM, S-adenosyl-L-homocysteine (SAH) is formed as a byproduct, which in turn is hydrolyzed to adenosine (Ado) and homocysteine (Hcy) by SAHase. The crystal structure of BeSAHase, an SAHase from Bradyrhizobium elkanii, which is a nitrogen-fixing bacterial symbiont of legume plants, was determined at 1.7 Å resolution, showing the domain organization (substrate-binding domain, NAD(+) cofactor-binding domain and dimerization domain) of the subunits. The protein crystallized in its biologically relevant tetrameric form, with three subunits in a closed conformation enforced by complex formation with the Ado product of the enzymatic reaction. The fourth subunit is ligand-free and has an open conformation. The BeSAHase structure therefore provides a unique snapshot of the domain movement of the enzyme induced by the binding of its natural ligands.
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Manszewski
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Kriti
authors.initials: K
authors.lastname: Singh
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Imiolczyk
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Jaskolski
mesh_terms: D000241:Adenosine / Q000737:chemistry / Q000378:metabolism; D043383:Adenosylhomocysteinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D055162:Biocatalysis; D020369:Bradyrhizobium / Q000737:chemistry* / Q000201:enzymology; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006710:Homocysteine / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000737:chemistry* / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D006710:Homocysteine; D009243:NAD; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D043383:Adenosylhomocysteinase; D000241:Adenosine
keywords: S-adenosyl-l-homocysteine; S-adenosyl-l-homocysteine hydrolase; S-adenosyl-l-methionine; adenosine; homocysteine; nicotinamide adenine dinucleotide; nitrogen fixation; plant–bacteria interactions