Structural comparison of the isomeric dipeptides L-glycyl-L-methionine and L-methionyl-L-glycine

What is it about?

The oxidation of methionine peptides can lead to increased biological stress and inflammation. The way peptides are shaped influences their oxidation and the intermediate products formed. This study reports the crystal structures of two similar dipeptides: Gly-Met and Met-Gly. Both exist as zwitterions, meaning they have both positive and negative charges. Gly-Met has a straight structure, while Met-Gly has a kinked shape. Methionine and its peptides are important in protein oxidation. Methionine's sulfur atom can be easily oxidized, forming reactive radicals that can damage proteins and lead to diseases. The position of methionine in a peptide affects its oxidation. For example, Met-Gly forms stable radicals not seen in Gly-Met, and they dissociate differently when collided with radicals. Factors influencing methionine peptide oxidation include the peptide’s structure, methionine's position, surrounding groups, the type of oxidants, and solvent properties. Peptides can have different shapes depending on the environment. This report highlights the zwitterionic forms of Gly-Met and Met-Gly, suggesting that differences in peptide shape may explain varying oxidation behaviors observed in studies.

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Photo by Choong Deng Xiang on Unsplash

Photo by Choong Deng Xiang on Unsplash

Why is it important?

Understanding the oxidation of methionine peptides is crucial because it helps explain how oxidative stress contributes to biological damage and inflammation. Methionine, a key amino acid in proteins, is easily oxidized, leading to the formation of harmful radicals that can damage proteins and disrupt their function. This damage is linked to various inflammatory and age-related diseases. Studying the crystal structures of methionine-containing peptides, such as Gly-Met and Met-Gly, provides insight into how their shape and conformation influence oxidation. Knowing the differences in their structures helps us understand why they oxidize differently and form different reaction intermediates. This knowledge is vital for developing strategies to prevent or mitigate oxidative damage in proteins, which could lead to new treatments for diseases related to oxidative stress and inflammation. Additionally, recognizing how factors like peptide structure, methionine position, and environmental conditions affect oxidation can help in designing more stable peptides for therapeutic and industrial applications. Overall, this research enhances our understanding of protein oxidation mechanisms and their implications for health and disease.

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