8EAC

Thermus thermophilus methylenetetrahydrofolate reductase

Summary for 8EAC

• Entry DOI: 10.2210/pdb8eac/pdb
• Descriptor: Methylenetetrahydrofolate reductase, FLAVIN-ADENINE DINUCLEOTIDE (3 entities in total)
• Functional Keywords: tim barrel, flavin, oxidoreductase
• Biological source: Thermus thermophilus HB8
• Total number of polymer chains: 2
• Total formula weight: 66887.32

Authors

Yamada, K.,Koutmos, M. (deposition date: 2022-08-28, release date: 2023-01-18, Last modification date: 2023-10-25)

Primary citation

Yamada, K.,Mendoza, J.,Koutmos, M.
5-Formyltetrahydrofolate promotes conformational remodeling in a methylenetetrahydrofolate reductase active site and inhibits its activity.
J.Biol.Chem., 299:102855-102855, 2022

PubMed Abstract: The flavoprotein methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of N5, N10-methylenetetrahydrofolate (CH-Hfolate) to N5-methyltetrahydrofolate (CH-Hfolate), committing a methyl group from the folate cycle to the methionine one. This committed step is the sum of multiple ping-pong electron transfers involving multiple substrates, intermediates, and products all sharing the same active site. Insight into folate substrate binding is needed to better understand this multifunctional active site. Here, we performed activity assays with Thermus thermophilus MTHFR (tMTHFR), which showed pH-dependent inhibition by the substrate analog, N5-formyltetrahydrofolate (CHO-Hfolate). Our crystal structure of a tMTHFR•CHO-Hfolate complex revealed a unique folate-binding mode; tMTHFR subtly rearranges its active site to form a distinct folate-binding environment. Formation of a novel binding pocket for the CHO-Hfolate p-aminobenzoic acid moiety directly affects how bent the folate ligand is and its accommodation in the active site. Comparative analysis of the available active (FAD- and folate-bound) MTHFR complex structures reveals that CHO-Hfolate is accommodated in the active site in a conformation that would not support hydride transfer, but rather in a conformation that potentially reports on a different step in the reaction mechanism after this committed step, such as CH-Hfolate ring-opening. This active site remodeling provides insights into the functional relevance of the differential folate-binding modes and their potential roles in the catalytic cycle. The conformational flexibility displayed by tMTHFR demonstrates how a shared active site can use a few amino acid residues in lieu of extra domains to accommodate chemically distinct moieties and functionalities.

PubMed: 36592927
DOI: 10.1016/j.jbc.2022.102855

Experimental method

X-RAY DIFFRACTION (1.9 Å)