Plant Biology
Structural and Functional Studies of Pavine N-Methyltransferase from Thalictrum flavum Reveal Novel Insights into Substrate Recognition and Catalytic Mechanism
Benzylisoquinoline alkaloids (BIAs) are produced in a wide variety of plants and include many common analgesic, antitussive, and anticancer compounds. Several members of a distinct family of S-adenosylmethionine (SAM)-dependent N-methyltransferases (NMTs) play critical roles in BIA biosynthesis, but the molecular basis of substrate recognition and catalysis is not known for NMTs involved in BIA metabolism. To address this issue, the crystal structure of pavine NMT from Thalictrum flavum was solved using selenomethionine-substituted protein (dmin = 2.8 Å).Structural Determinants for Substrate Binding and Catalysis in Triphosphate Tunnel Metalloenzymes
Background: Triphosphate tunnel metalloenzymes carry out diverse enzymatic reactions.Results: Two metal co-factors are identified involved in substrate binding and in catalysis.Conclusion: A unified catalytic mechanism is proposed and biochemically investigated.Significance: The functional diversity of TTM enzymes is rationalized by a common mechanism that allows very different substrates to be bound and processed.
