A peptide-crosslinking approach identifies HSPA8 and PFKL as selective interactors of an actin-derived peptide containing reduced and oxidized methionine.

The oxidation of methionine to methionine sulfoxide occurs under conditions of cellular oxidative stress, and modulates the function of a diverse array of proteins. Enzymatic systems that install and reverse the methionine sulfoxide modifications have been characterized, however, little is known about potential readers of this oxidative modification. Here, we apply a peptide-crosslinking approach to identify proteins that are able to differentially interact with reduced and oxidized methionine-containing peptides. Specifically, we generated a photo-crosslinking peptide derived from actin, which contains two sites of methionine oxidation, M44 and M47. Our proteomic studies identified heat shock proteins, including HSPA8, as selective for the reduced methionine-containing peptide, whereas the phosphofructokinase isoform, PFKL, preferentially interacts with the oxidized form. We then demonstrate that the favored interaction of PFKL with oxidized methionine is also observed in the full-length actin protein, suggesting a role of methionine oxidation in regulating the actin-PFKL interaction in cells. Our studies demonstrate the potential to identify proteins that can differentiate between reduced and oxidized methionine and thereby mediate downstream protein functions under conditions of oxidative stress. Furthermore, given that numerous sites of methionine oxidation have now been identified, these studies set the stage to identify putative readers of methionine oxidation on other protein targets.