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| Content Provider | Springer Nature Link |
|---|---|
| Author | Kumar, Maj Hirao, Hajime Kozlowski, Pawel M. |
| Copyright Year | 2012 |
| Abstract | A detailed computational analysis employing density functional theory (DFT), atoms in molecules, and quantum mechanics/molecular mechanics (QM/MM) tools has been performed to investigate the primary coordination environment of cob(I)alamin (Co+Cbx), which is a ubiquitous B12 intermediate in methyltransferases and ATP:corrinoid adenosyltransferases. The DFT calculations suggest that the simplified (Co+Cbl) as well as the complete (Co+Cbi) complexes can adapt to the square pyramidal or octahedral coordination geometry owing to the unconventional H-bonding between the Co+ ion and its axial ligands. These Co+–H bonds contain appreciable amounts of electrostatic, charge transfer, long-range correlation, and dispersion components. The computed reduction potentials of the Co2+/Co+ couple imply that the Co+–H(H2O) interaction causes a greater anodic shift [5–98 mV vs. the normal hydrogen electrode (NHE) in chloroform solvent] than the analogous Co+–H(imidazole) interaction (1 mV vs. NHE) in the reduction potential of the Co2+/Co+ couple. This may explain why a β-axial H2O ligand has specifically been found in the active sites of certain methyltransferases. The QM/MM analysis of methionine synthase bound Co+Cbx (Protein Data Bank ID 1BMT, resolution 3.0 Å) indicates that the enzyme-bound Co+Cbx can also form a Co+–H bond, but can only exist in square pyramidal form because of the steric constraints imposed by the cellular environment. The present calculations thus support a recently proposed alternate mechanism for the enzyme-bound Co2+/Co+ reduction that involves the conversion of square pyramidal Co2+Cbx into square pyramidal Co+Cbx (Kumar and Kozlowski in Angew. Chem. Int. Ed. 50:8702–8705, 2011). |
| Starting Page | 1107 |
| Ending Page | 1121 |
| Page Count | 15 |
| File Format | |
| ISSN | 09498257 |
| Journal | JBIC Journal of Biological Inorganic Chemistry |
| Volume Number | 17 |
| Issue Number | 7 |
| e-ISSN | 14321327 |
| Language | English |
| Publisher | Springer-Verlag |
| Publisher Date | 2012-08-08 |
| Publisher Place | Berlin, Heidelberg |
| Access Restriction | One Nation One Subscription (ONOS) |
| Subject Keyword | Methyltransferase Cob(I)alamin Co+–H interaction DFT-D Co2+/Co+ reduction Biochemistry Microbiology |
| Content Type | Text |
| Resource Type | Article |
| Subject | Biochemistry Inorganic Chemistry |
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