4ojt
From Proteopedia
Helicobacter pylori MTAN complexed with S-ribosylhomocysteine and adenine
Structural highlights
FunctionMQMTN_HELPJ Catalyzes the direct conversion of aminodeoxyfutalosine (AFL) into dehypoxanthine futalosine (DHFL) and adenine via the hydrolysis of the N-glycosidic bond; this reaction seems to represent an essential step in the menaquinone biosynthesis pathway in Helicobacter species. Also catalyzes the hydrolysis of 5'-methylthioadenosine (MTA) to adenine and 5'-methylthioribose. Can also probably use S-adenosylhomocysteine (SAH) as substrate, leading to adenine and S-ribosylhomocysteine. These other activities highlight the tremendous versatility of the enzyme, which also plays key roles in S-adenosylmethionine recycling and in the biosynthesis of the quorum-sensing molecule autoinducer-2.[1] [2] Publication Abstract from PubMedThe bacterial 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) enzyme is a multifunctional enzyme that catalyzes the hydrolysis of the N-ribosidic bond of at least four different adenosine-based metabolites: S-adenosylhomocysteine (SAH), 5'-methylthioadenosine (MTA), 5'-deoxyadenosine (5'-DOA), and 6-amino-6-deoxyfutalosine. These activities place the enzyme at the hub of seven fundamental bacterial metabolic pathways: S-adenosylmethionine (SAM) utilization, polyamine biosynthesis, the purine salvage pathway, the methionine salvage pathway, the SAM radical pathways, autoinducer-2 biosynthesis, and menaquinone biosynthesis. The last pathway makes MTAN essential for Helicobacter pylori viability. Although structures of various bacterial and plant MTANs have been described, the interactions between the homocysteine moiety of SAH and the 5'-alkylthiol binding site of MTAN have never been resolved. We have determined crystal structures of an inactive mutant form of H. pylori MTAN bound to MTA and SAH to 1.63 and 1.20 A, respectively. The active form of MTAN was also crystallized in the presence of SAH, allowing the determination of the structure of a ternary enzyme-product complex resolved at 1.50 A. These structures identify interactions between the homocysteine moiety and the 5'-alkylthiol binding site of the enzyme. This information can be leveraged for the development of species-specific MTAN inhibitors that prevent the growth of H. pylori. Crystal structures of the Helicobacter pylori MTAN enzyme reveal specific interactions between S-adenosylhomocysteine and the 5'-alkylthio binding subsite.,Mishra V, Ronning DR Biochemistry. 2012 Dec 4;51(48):9763-72. doi: 10.1021/bi301221k. Epub 2012 Nov, 20. PMID:23148563[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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