Structural Basis for Putrescine Activation of Human S-Adenosylmethionine Decarboxylase
Open Access
- 17 November 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 47 (50), 13404-13417
- https://doi.org/10.1021/bi801732m
Abstract
Putrescine (1,4-diaminobutane) activates the autoprocessing and decarboxylation reactions of human S-adenosylmethionine decarboxylase (AdoMetDC), a critical enzyme in the polyamine biosynthetic pathway. In human AdoMetDC, putrescine binds in a buried pocket containing acidic residues Asp174, Glu178, and Glu256. The pocket is away from the active site but near the dimer interface; however, a series of hydrophilic residues connect the putrescine binding site and the active site. Mutation of these acidic residues modulates the effects of putrescine. D174N, E178Q, and E256Q mutants were expressed and dialyzed to remove putrescine and studied biochemically using X-ray crystallography, UV-CD spectroscopy, analytical ultracentrifugation, and ITC binding studies. The results show that the binding of putrescine to the wild type dimeric protein is cooperative. The D174N mutant does not bind putrescine, and the E178Q and E256Q mutants bind putrescine weakly with no cooperativity. The crystal structure of the mutants with and without putrescine and their complexes with S-adenosylmethionine methyl ester were obtained. Binding of putrescine results in a reorganization of four aromatic residues (Phe285, Phe315, Tyr318, and Phe320) and a conformational change in the loop 312−320. The loop shields putrescine from the external solvent, enhancing its electrostatic and hydrogen bonding effects. The E256Q mutant with putrescine added shows an alternate conformation of His243, Glu11, Lys80, and Ser229, the residues that link the active site and the putrescine binding site, suggesting that putrescine activates the enzyme through electrostatic effects and acts as a switch to correctly orient key catalytic residues.Keywords
This publication has 50 references indexed in Scilit:
- Allosteric regulation of an essential trypanosome polyamine biosynthetic enzyme by a catalytically dead homologProceedings of the National Academy of Sciences of the United States of America, 2007
- Multi-centre Phase II trial of the polyamine synthesis inhibitor SAM486A (CGP48664) in patients with metastatic melanomaInvestigational New Drugs, 2005
- Coot: model-building tools for molecular graphicsActa Crystallographica Section D-Biological Crystallography, 2004
- A perspective of polyamine metabolismBiochemical Journal, 2003
- Population Pharmacokinetics/Toxicodynamics (PK/TD) Relationship of SAM486A in Phase I Studies in Patients with Advanced CancersThe Journal of Clinical Pharmacology, 2000
- [20] Processing of X-ray diffraction data collected in oscillation modeMethods in Enzymology, 1997
- Improved methods for building protein models in electron density maps and the location of errors in these modelsActa Crystallographica Section A Foundations of Crystallography, 1991
- Partial molar volumes of polypeptides and their constituent groups in aqueous solution over a broad temperature rangePeptide Science, 1990
- Methionine Adenosyltransferase ( S ‐Adenosylmethionine Synthetase) and S ‐Adenosylmethionine DecarboxylasePublished by Wiley ,1984
- Correction of light‐scattering errors in spectrophotometric protein determinationsPeptide Science, 1971