title: Structure of Staphylococcus aureus 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase.
abstract: 5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) catalyzes the irreversible cleavage of the glycosidic bond in 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH) and plays a key role in four metabolic processes: biological methylation, polyamine biosynthesis, methionine recycling and bacterial quorum sensing. The absence of the nucleosidase in mammalian species has implicated this enzyme as a target for antimicrobial drug design. MTAN from the pathogenic bacterium Staphylococcus aureus (SaMTAN) has been kinetically characterized and its structure has been determined in complex with the transition-state analogue formycin A (FMA) at 1.7 A resolution. A comparison of the SaMTAN-FMA complex with available Escherichia coli MTAN structures shows strong conservation of the overall structure and in particular of the active site. The presence of an extra water molecule, which forms a hydrogen bond to the O4' atom of formycin A in the active site of SaMTAN, produces electron withdrawal from the ribosyl group and may explain the lower catalytic efficiency that SaMTAN exhibits when metabolizing MTA and SAH relative to the E. coli enzyme. The implications of this structure for broad-based antibiotic design are discussed.
authors.affiliation: Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Karen K W
authors.initials: KK
authors.lastname: Siu
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Lee
authors.forename: G David
authors.initials: GD
authors.lastname: Smith
authors.forename: Cathy
authors.initials: C
authors.lastname: Horvatin-Mrakovcic
authors.forename: P Lynne
authors.initials: PL
authors.lastname: Howell
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D003839:Deoxyadenosines / Q000737:chemistry* / Q000378:metabolism; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology; D005573:Formycins / Q000378:metabolism; D006860:Hydrogen Bonding; D007700:Kinetics; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012435:S-Adenosylhomocysteine / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013211:Staphylococcus aureus / Q000201:enzymology*; D013872:Thionucleosides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003839:Deoxyadenosines; D004791:Enzyme Inhibitors; D005573:Formycins; D013872:Thionucleosides; C008500:5'-methylthioadenosine; C034550:formycin; D012435:S-Adenosylhomocysteine; D009699:N-Glycosyl Hydrolases; C019606:adenosylhomocysteine nucleosidase