Sacrificial Methionine Residues Protect Active-Site Histidines From Oxidation.
- 1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Abstract
Histidine is the most common residue in enzymic active sites because of the chemical versatility of its imidazole side chain, but is also highly vulnerable to oxidative damage. Here, we demonstrate that methionine residues in secretory ribonucleases such as bovine RNase A serve as sacrificial antioxidants that protect active-site histidines. In the human homolog RNase 1, five methionine residues cluster near the catalytic histidines His12 and His119, which serve as a base and an acid, respectively, during RNA cleavage. Bioinformatic analyses reveal that these methionines are conserved across the RNase A superfamily and adopt S-aryl motifs with proximal aromatic residues that modulate the electron density at sulfur and thereby tune the susceptibility of methionine to oxidation. Chemoselective labeling of methionine with an oxaziridine probe increased the vulnerability of RNase 1 to oxidation-induced inactivation, implicating Met29 and Met35 as protective residues. Total chemical synthesis of an RNase 1 variant in which these residues were replaced by norleucine, a sulfur-free isostere of methionine, corroborated their protective role. A similar arrangement of methionines is present in unrelated secretory proteins, including serine proteases and calprotectin, suggesting a broadly recurring protective strategy.
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BibTeX
@article{wralstad2026sacrificial,
title = {{Sacrificial Methionine Residues Protect Active-Site Histidines From Oxidation.}},
author = {Evans C Wralstad and Jessica Sayers and Giulio Fittolani and David Sarabia-Castillo and Alex J Callahan and Bradley L Pentelute and Ronald T Raines},
journal = {Angewandte chemie novit},
year = {2026},
month = sep,
doi = {10.1002/anov.70034},
url = {https://europepmc.org/article/MED/42928774},
note = {CC BY},
}
RIS
TY - JOUR
TI - Sacrificial Methionine Residues Protect Active-Site Histidines From Oxidation.
AU - Evans C Wralstad
AU - Jessica Sayers
AU - Giulio Fittolani
AU - David Sarabia-Castillo
AU - Alex J Callahan
AU - Bradley L Pentelute
AU - Ronald T Raines
PY - 2026
DA - 2026/09/17
JO - Angewandte chemie novit
DO - 10.1002/anov.70034
UR - https://europepmc.org/article/MED/42928774
AB - Histidine is the most common residue in enzymic active sites because of the chemical versatility of its imidazole side chain, but is also highly vulnerable to oxidative damage. Here, we demonstrate that methionine residues in secretory ribonucleases such as bovine RNase A serve as sacrificial antioxidants that protect active-site histidines. In the human homolog RNase 1, five methionine residues cluster near the catalytic histidines His12 and His119, which serve as a base and an acid, respectively, during RNA cleavage. Bioinformatic analyses reveal that these methionines are conserved across the RNase A superfamily and adopt S-aryl motifs with proximal aromatic residues that modulate the electron density at sulfur and thereby tune the susceptibility of methionine to oxidation. Chemoselective labeling of methionine with an oxaziridine probe increased the vulnerability of RNase 1 to oxidation-induced inactivation, implicating Met29 and Met35 as protective residues. Total chemical synthesis of an RNase 1 variant in which these residues were replaced by norleucine, a sulfur-free isostere of methionine, corroborated their protective role. A similar arrangement of methionines is present in unrelated secretory proteins, including serine proteases and calprotectin, suggesting a broadly recurring protective strategy.
SN - 2510-9537
ER -