9dth

Publication Abstract from PubMed

Cross-linked protein residues exist as enzyme cofactors to enable or enhance catalytic activities. Despite their importance in nature, the chemical identity of the cross-links is limited to certain amino acid combinations, whose function and the formation mechanism remain insufficiently understood due to the difficulty in isolating native enzymes without the cross-links. Herein, we report the formation and characterization of both His-Tyr and His-His cross-links under oxidative enzymatic turnover conditions in L29H/F33Y/F43H Mb, a structural and functional model of heme-copper oxidase (HCO). The connectivity of the cross-link was characterized as N(epsilon2)(His29)-C(delta2)(His43) by mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR). Interestingly, formation of the cross-link significantly enhances the oxygen reduction activity of the enzyme at neutral or basic pH with higher product specificity. X-ray crystallography has identified a novel Tyr-His cross-link through a Tyr-O-His linkage. Our mechanistic studies indicate the involvement of high-valent heme-iron and the neighboring tyrosine in an oxidative self-processing pathway to generate the cross-link. This work serves as a new example while providing insights into the enzyme cross-link formation, allowing the design of artificial biocatalysts containing these novel cross-links with higher activity and pH adaptability.

A Post-translational Histidine-Histidine Cross-Link Enhances Enzymatic Oxygen Reduction Activity with Greater pH Adaptability.,Liu Y, Vilbert AC, Ghosh B, Young RP, Merkley ED, Mukherjee A, Phan L, Van Stappen C, Baghi-Damodaran A, Miner KD, Adkins J, Cort J, Lu Y J Am Chem Soc. 2025 Oct 6. doi: 10.1021/jacs.5c12710. PMID:41047894^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.