Work

Mining the cysteine-motif repertoire of airway mucins reveals redox-active mucolytic peptides

Year: 2026

Type: preprint

Abstract: Muco-obstructive lung diseases are characterized by hyper concentrated airway mucus in which gel-forming mucins form mechanically reinforced polymer networks. Thiol-based mucolytics can reduce disulfide bonds within these networks, but clinically used monothiols show limited potency, whereas stronger reducing agents are constrained by instability and toxicity. Here, we systematically mined the major airway mucins MUC5B and MUC5AC for closely spaced cysteine motifs and screened the resulting mucin-derived peptide library for redox activity, oxidation stability, solubility, epithelial compatibility, and mucolytic activity. The identified Cys–[X]n–Cys peptides displayed pronounced sequence- and pH-dependent thioldisulfide exchange capabilities, with many peptides reacting faster than monothiol controls and several exhibiting reactivity approaching or superior to dithiothreitol (DTT). Reactivity was governed by the combined effects of thiol number, apparent thiol pKa, and local motif architecture rather than by a single physicochemical descriptor. Analysis of free-thiol stability and oxidation products further revealed sequence-dependent access to distinct intra- and intermolecular disulfide states. Together, these measurements provide a systematic sequence-redox framework for understanding how closely spaced cysteine motifs tune thioldisulfide exchange, with implications for the design of redox-active peptides and for understanding how local cysteine sequence environments may contribute to oxidative protein folding. Developability profiling identified soluble, reduced-thiol-stable, and epithelialcompatible candidates. Selected peptides reduced high-molecular-weight MUC5B multimers in cystic fibrosis mucus and MUC5AC multimers in asthma mucus, with activities in the range of DTT and greater than NAC under the tested conditions. These peptides were active in both pathological and healthy mucus, while showing compound-dependent differences in their concentration-response profiles across mucus environments. Our findings point at airway mucins as a source of redox-active peptide candidates with potential for mucolytic therapy and provide a broadly applicable resource for relating cysteine-motif sequence to disulfideexchange behavior.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15009830/v1