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The role of the Met20 loop in the hydride transfer in Escherichia coli dihydrofolate reductase
| Content Provider | Scilit |
|---|---|
| Author | Mhashal, Anil R. Vardi-Kilshtain, Alexandra Kohen, Amnon Major, Dan Thomas |
| Copyright Year | 2017 |
| Description | Journal: Journal of Biological Chemistry A key question concerning the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) is whether the $Met^{20}$ loop is dynamically coupled to the chemical step during catalysis. A more basic, yet unanswered question is whether the $Met^{20}$ loop adopts a closed conformation during the chemical hydride transfer step. To examine the most likely conformation of the $Met^{20}$ loop during the chemical step, we studied the hydride transfer in wild type (WT) ecDHFR using hybrid quantum mechanics-molecular mechanics free energy simulations with the $Met^{20}$ loop in a closed and disordered conformation. Additionally, we investigated three mutant forms (I14X; X = Val, Ala, Gly) of the enzyme that have increased active site flexibility and donor-acceptor distance dynamics in closed and disordered $Met^{20}$ loop states. We found that the conformation of the $Met^{20}$ loop has a dramatic effect on the ordering of active site hydration, although the $Met^{20}$ loop conformation only has a moderate effect on the hydride transfer rate and donor-acceptor distance dynamics. Finally, we evaluated the $pK_{a}$ of the substrate N5 position in closed and disordered $Met^{20}$ loop states and found a strong correlation between N5 basicity and the conformation of the $Met^{20}$ loop. |
| Related Links | http://www.jbc.org/content/292/34/14229.full.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5572915/pdf http://www.jbc.org/article/S0021925820342368/pdf |
| Ending Page | 14239 |
| Page Count | 11 |
| Starting Page | 14229 |
| ISSN | 00219258 |
| e-ISSN | 1083351X |
| DOI | 10.1074/jbc.m117.777136 |
| Journal | Journal of Biological Chemistry |
| Issue Number | 34 |
| Volume Number | 292 |
| Language | English |
| Publisher | Elsevier BV |
| Publisher Date | 2017-08-01 |
| Access Restriction | Open |
| Subject Keyword | Journal: Journal of Biological Chemistry Biochemistry and Molecular Biology Dihydrofolate Reductase Enzyme Catalysis Molecular Dynamics Protein Dynamic Quantum Chemistry |
| Content Type | Text |
| Resource Type | Article |
| Subject | Cell Biology Biochemistry Molecular Biology |
