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- Title
Insights in 17β-HSD1 Enzyme Kinetics and Ligand Binding by Dynamic Motion Investigation.
- Authors
Negri, Matthias; Recanatini, Maurizio; Hartmann, Rolf W.
- Abstract
Background: Bisubstrate enzymes, such as 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1), exist in solution as an ensemble of conformations. 17β-HSD1 catalyzes the last step of the biosynthesis of estradiol and, thus, it is a potentially attractive target for breast cancer treatment. Methodology/Principal Findings: To elucidate the conformational transitions of its catalytic cycle, a structural analysis of all available crystal structures was performed and representative conformations were assigned to each step of the putative kinetic mechanism. To cover most of the conformational space, all-atom molecular dynamic simulations were performed using the four crystallographic structures best describing apoform, opened, occluded and closed state of 17β-HSD1 as starting structures. With three of them, binary and ternary complexes were built with NADPH and NADPH-estrone, respectively, while two were investigated as apoform. Free energy calculations were performed in order to judge more accurately which of the MD complexes describes a specific kinetic step. Conclusions/Significance: Remarkably, the analysis of the eight long range trajectories resulting from this multi-trajectory/- complex approach revealed an essential role played by the backbone and side chain motions, especially of the βFaG9-loop, in cofactor and substrate binding. Thus, a selected-fit mechanism is suggested for 17β-HSD1, where ligand-binding induced concerted motions of the FG-segment and the C-terminal part guide the enzyme along its preferred catalytic pathway. Overall, we could assign different enzyme conformations to the five steps of the random bi-bi kinetic cycle of 17β-HSD1 and we could postulate a preferred pathway for it. This study lays the basis for more-targeted biochemical studies on 17β-HSD1, as well as for the design of specific inhibitors of this enzyme. Moreover, it provides a useful guideline for other enzymes, also characterized by a rigid core and a flexible region directing their catalysis.
- Subjects
ENZYME kinetics; LIGAND binding (Biochemistry); DYNAMICS; CONFORMATIONAL analysis; CATALYSIS; STRUCTURAL analysis (Engineering); BREAST cancer treatment; CRYSTALLOGRAPHY; LINEAR free energy relationship; ENZYME inhibitors
- Publication
PLoS ONE, 2010, Vol 5, Issue 8, p1
- ISSN
1932-6203
- Publication type
Article
- DOI
10.1371/journal.pone.0012026