The enzyme serine hydroxymethyltransferase (SHMT) plays a key role in folate metabolism and is conserved in all kingdoms of life. SHMT is a pyridoxal 5’-phosphate (PLP) - dependent enzyme that catalyzes the conversion of L-serine and (6S)-tetrahydrofolate to glycine and 5,10-methylene tetrahydrofolate. Crystal structures of multiple members of the SHMT family have shown that the enzyme has a single conserved cis proline, which is located near the active site. Here, we have characterized a Pro to Ser amino acid variant (P285S) that affects this conserved cis proline in soybean SHMT8. P285S was identified as one of a set of mutations that affect the resistance of soybean to the agricultural pathogen soybean cyst nematode. We find that replacement of Pro285 by serine eliminates PLP-mediated catalytic activity of SHMT8, reduces folate binding, decreases enzyme stability, and affects the dimer-tetramer ratio of the enzyme in solution. Crystal structures at 1.9 – 2.2 Å resolution reveal a local reordering of the polypeptide chain that extends an a-helix and shifts a turn region into the active site. This results in a dramatically perturbed PLP-binding pose, where the ring of the cofactor is flipped by ~180° with concomitant loss of conserved enzyme-PLP interactions. A nearby region of the polypeptide becomes disordered, evidenced by missing electron density for ~10 residues. These structural perturbations are consistent with the loss of enzyme activity and folate binding and underscore the important role of the Pro285 cis-peptide in SHMT structure and function.
This content will become publicly available on May 17, 2025
- Award ID(s):
- 2203593
- PAR ID:
- 10517098
- Editor(s):
- He, Chuan
- Publisher / Repository:
- ACS Publications
- Date Published:
- Journal Name:
- ACS Chemical Biology
- Volume:
- 19
- Issue:
- 5
- ISSN:
- 1554-8929
- Page Range / eLocation ID:
- 1066-1081
- Subject(s) / Keyword(s):
- ornithine aminotransferase inhibition carcinoma pyridoxalphosphate
- Format(s):
- Medium: X Size: N/A Other: N/A
- Size(s):
- N/A
- Sponsoring Org:
- National Science Foundation
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