1
|
Ghebreamlak S, Stoian SA, Lees NS, Cronin B, Smith F, Ross MO, Telser J, Hoffman BM, Duin EC. The Active-Site [4Fe-4S] Cluster in the Isoprenoid Biosynthesis Enzyme IspH Adopts Unexpected Redox States during Ligand Binding and Catalysis. J Am Chem Soc 2024; 146:3926-3942. [PMID: 38291562 DOI: 10.1021/jacs.3c11674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
(E)-4-Hydroxy-3-methylbut-2-enyl diphosphate reductase, or IspH (formerly known as LytB), catalyzes the terminal step of the bacterial methylerythritol phosphate (MEP) pathway for isoprene synthesis. This step converts (E)-4-hydroxy-3-methylbut-2-enyl diphosphate (HMBPP) into one of two possible isomeric products, either isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). This reaction involves the removal of the C4 hydroxyl group of HMBPP and addition of two electrons. IspH contains a [4Fe-4S] cluster in its active site, and multiple cluster-based paramagnetic species of uncertain redox and ligation states can be detected after incubation with reductant, addition of a ligand, or during catalysis. To characterize the clusters in these species, 57Fe-labeled samples of IspH were prepared and studied by electron paramagnetic resonance (EPR), 57Fe electron-nuclear double resonance (ENDOR), and Mössbauer spectroscopies. Notably, this ENDOR study provides a rarely reported, complete determination of the 57Fe hyperfine tensors for all four Fe ions in a [4Fe-4S] cluster. The resting state of the enzyme (Ox) has a diamagnetic [4Fe-4S]2+ cluster. Reduction generates [4Fe-4S]+ (Red) with both S = 1/2 and S = 3/2 spin ground states. When the reduced enzyme is incubated with substrate, a transient paramagnetic reaction intermediate is detected (Int) which is thought to contain a cluster-bound substrate-derived species. The EPR properties of Int are indicative of a 3+ iron-sulfur cluster oxidation state, and the Mössbauer spectra presented here confirm this. Incubation of reduced enzyme with the product IPP induced yet another paramagnetic [4Fe-4S]+ species (Red+P) with S = 1/2. However, the g-tensor of this state is commonly associated with a 3+ oxidation state, while Mössbauer parameters show features typical for 2+ clusters. Implications of these complicated results are discussed.
Collapse
Affiliation(s)
- Selamawit Ghebreamlak
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
| | - Sebastian A Stoian
- Department of Chemistry, University of Idaho, 875 Perimeter Drive, MS 2343 Moscow, Idaho 83844, United States
| | - Nicholas S Lees
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Bryan Cronin
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
| | - Forrest Smith
- Department of Drug Discovery & Development, Auburn University, 4306 Walker Building, Auburn, Alabama 36849, United States
| | - Matthew O Ross
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, Illinois 60605, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Evert C Duin
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
| |
Collapse
|
2
|
Abdalla JAB, Bowen AM, Bell SG, Wong LL, Timmel CR, Harmer J. Characterisation of the paramagnetic [2Fe–2S]+ centre in palustrisredoxin-B (PuxB) from Rhodopseudomonas palustris CGA009: g-matrix determination and spin coupling analysis. Phys Chem Chem Phys 2012; 14:6526-37. [DOI: 10.1039/c2cp24112a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
3
|
Cammack R, MacMillan F. Electron Magnetic Resonance of Iron–Sulfur Proteins in Electron-Transfer Chains: Resolving Complexity. METALS IN BIOLOGY 2010. [DOI: 10.1007/978-1-4419-1139-1_2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|