Dynamic inter-domain transformations mediate the allosteric regulation of human 5, 10-methylenetetrahydrofolate reductase

• Published in: Nature communications Vol. 15; no. 1; p. 3248
• Main Authors: Blomgren, Linnea K. M., Huber, Melanie, Mackinnon, Sabrina R., Bürer, Céline, Baslé, Arnaud, Yue, Wyatt W., Froese, D. Sean, McCorvie, Thomas J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15-04-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 101/28; 5, 10-Methylenetetrahydrofolate reductase (FADH2); 631/45/173; 631/45/607; 631/535/1258/1259; 631/57; 82/80; Acoustic microscopes; Allosteric properties; Allosteric Regulation; Asymmetry; Binding sites; Catalysis; Cellular structure; Conformation; Cryoelectron Microscopy; Crystal structure; Electron microscopy; Enzymatic activity; Enzymes; Feedback inhibition; Flexibility; Folic acid; Homocysteine; Humanities and Social Sciences; Humans; Inserts; L-Homocysteine; Methionine; Methylation; Methylenetetrahydrofolate reductase; Methylenetetrahydrofolate Reductase (NADPH2) - chemistry; Microscopy; multidisciplinary; Proteins; Reductases; Regulatory mechanisms (biology); S-Adenosylmethionine - metabolism; Scanning acoustic microscopy; Science; Science (multidisciplinary); Signal transduction; Substrates; Symmetry
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-47174-y

5,10-methylenetetrahydrofolate reductase (MTHFR) commits folate-derived one-carbon units to generate the methyl-donor
s
-adenosyl-
l
-methionine (SAM). Eukaryotic MTHFR appends to the well-conserved catalytic domain (CD) a unique regulatory domain (RD) that confers feedback inhibition by SAM. Here we determine the cryo-electron microscopy structures of human MTHFR bound to SAM and its demethylated product
s
-adenosyl-
l
-homocysteine (SAH). In the active state, with the RD bound to a single SAH, the CD is flexible and exposes its active site for catalysis. However, in the inhibited state the RD pocket is remodelled, exposing a second SAM-binding site that was previously occluded. Dual-SAM bound MTHFR demonstrates a substantially rearranged inter-domain linker that reorients the CD, inserts a loop into the active site, positions Tyr404 to bind the cofactor FAD, and blocks substrate access. Our data therefore explain the long-distance regulatory mechanism of MTHFR inhibition, underpinned by the transition between dual-SAM and single-SAH binding in response to cellular methylation status.
Here the authors present the cryo-EM structure of active and inhibited human MTHFR, revealing a dynamic inhibitory mechanism dependent on dual SAM binding. The resulting closed conformation features an autoinhibitory element effectively blocking enzymatic activity.