3HCA

Crystal Structure of E185Q hPNMT in Complex With Octopamine and AdoHcy

Summary for 3HCA

• Entry DOI: 10.2210/pdb3hca/pdb
• Related: 1HNN 1N7I 1N7J 1YZ3 2AN3 2AN4 2AN5 2G70 2G71 2G72 2G8N 2OBF 2ONY 2ONZ 2OPB 3HCB 3HCC 3HCD 3HCE 3HCF
• Descriptor: Phenylethanolamine N-methyltransferase, S-ADENOSYL-L-HOMOCYSTEINE, 4-(2R-AMINO-1-HYDROXYETHYL)PHENOL, ... (5 entities in total)
• Functional Keywords: methyltransferase, catecholamine biosynthesis, polymorphism, s-adenosyl-l-methionine, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 2
• Total formula weight: 64827.21

Authors

Drinkwater, N.,Martin, J.L. (deposition date: 2009-05-06, release date: 2009-08-25, Last modification date: 2024-11-06)

Primary citation

Drinkwater, N.,Gee, C.L.,Puri, M.,Criscione, K.R.,McLeish, M.J.,Grunewald, G.L.,Martin, J.L.
Molecular recognition of physiological substrate noradrenaline by the adrenaline-synthesizing enzyme PNMT and factors influencing its methyltransferase activity.
Biochem.J., 422:463-471, 2009

PubMed Abstract: Substrate specificity is critically important for enzyme catalysis. In the adrenaline-synthesizing enzyme PNMT (phenylethanolamine N-methyltransferase), minor changes in substituents can convert substrates into inhibitors. Here we report the crystal structures of six human PNMT complexes, including the first structure of the enzyme in complex with its physiological ligand R-noradrenaline. Determining this structure required rapid soak methods because of the tendency for noradrenaline to oxidize. Comparison of the PNMT-noradrenaline complex with the previously determined PNMT-p-octopamine complex demonstrates that these two substrates form almost equivalent interactions with the enzyme and show that p-octopamine is a valid model substrate for PNMT. The crystal structures illustrate the adaptability of the PNMT substrate binding site in accepting multi-fused ring systems, such as substituted norbornene, as well as noradrenochrome, the oxidation product of noradrenaline. These results explain why only a subset of ligands recognized by PNMT are methylated by the enzyme; bulky substituents dictate the binding orientation of the ligand and can thereby place the acceptor amine too far from the donor methyl group for methylation to occur. We also show how the critical Glu(185) catalytic residue can be replaced by aspartic acid with a loss of only 10-fold in catalytic efficiency. This is because protein backbone movements place the Asp(185) carboxylate almost coincident with the carboxylate of Glu(185). Conversely, replacement of Glu(185) by glutamine reduces catalytic efficiency almost 300-fold, not only because of the loss of charge, but also because the variant residue does not adopt the same conformation as Glu(185).

PubMed: 19570037
DOI: 10.1042/BJ20090702

Experimental method

X-RAY DIFFRACTION (2.4 Å)