The methylglyoxal-derived hydroimidazolone isomer, MGH-1, is an abundant advanced glycation end-product (AGE) associated with disease and age-related disorders. As AGE formation occurs spontaneously and without an enzyme, it remains unknown why certain sites on distinct proteins become modified with specific AGEs. Here, we use a combinatorial peptide library to determine the chemical features that favor MGH-1. When properly positioned, tyrosine is found to play an active mechanistic role that facilitates MGH-1 formation. This work offers mechanistic insight connecting multiple AGEs, including MGH-1 and carboxyethylarginine (CEA), and reconciles the role of negative charge in influencing glycation outcomes. Further, this study provides clear evidence that glycation outcomes can be influenced through long- or medium-range cooperative interactions.
Fig: Glycation is a selective, nonenzymatic PTM: a Glycation is a nonenzymatic post-translational modification (PTM) that occurs preferentially at certain Arg or Lys residues on certain proteins. For instance, human serum albumin (HSA, PDBID:1E7I) possesses 87 possible glycation sites (blue). Only 12 of these are reported to be glycated, and one site (green), is reported to be the most reactive. Yet, it remains an open question as to how the surrounding microenvironment—a combination of sequence and structure—templates the exact glycation outcome. For instance, the reaction of Arg with methylglyoxal (MGO), one of the most potent and prevalent cellular glycating agents, can produce numerous advanced glycation end-products (AGEs). b These include the methylglyoxal-derived hydroimidazolone isomers (MGH-1,-2,-3), dihydroxyimidazolidine (MGH-DH), carboxyethylarginine (CEA), argpyrimidine (APY), and tetrahydropyrimidine (THP).
This work demonstrates that these chemical features also predictably template selective glycation on full-length protein targets expressed in mammalian cells. This information is vital for developing methods that control glycation in living cells and will enable the study of glycation as a functional post-translational modification.
McEwen, J.M., Fraser, S., Guir, A.L.S. et al. Synergistic sequence contributions bias glycation outcomes. Nat Commun 12, 3316 (2021). https://doi.org/10.1038/s41467-021-23625-8