Protein S-sulfhydration (forming -S-SH adducts from cysteine residues) is a newly defined oxidative posttranslational modification and plays an important role in H2S-mediated signaling pathways. In this study we report the first selective, “tag-switch” method which can directly label protein S-sulfhydrated residues by forming stable thioether conjugates. Furthermore we demonstrate that H2S alone cannot lead to S-sulfhydration and that the two possible physiological mechanisms include reaction with protein sulfenic acids (P-SOH) or the involvement of metal centers which would facilitate the oxidation of H2S to HSC.

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Hydrogen sulfide (H2S) has emerged as new member of the gaseous transmitter family of signaling molecules and appears to play a regulatory role in the cardiovascular and nervous systems. Recent studies suggest that protein cysteine S-sulfhydration may function as a mechanism for transforming the H2S signal into a biological response. However, selective detection of S-sulfhydryl modifications is challenging since the persulfide group (RSSH) exhibits reactivity akin to other sulfur species, especially thiols. A modification of the biotin switch technique, using S-methyl methanethiosulfonate (MMTS) as an alkylating reagent, was recently used to identify a large number of proteins that may undergo S-sulfhydration, but the underlying mechanism of chemical detection was not fully explored. To address this key issue, we have developed a protein persulfide model and analog of MMTS, S-4-bromobenzyl methanethiosulfonate (BBMTS). Using these new reagents, we investigated the chemistry in the modified biotin switch method and examined the reactivity of protein persulfides toward different electrophile/nucleophile species. Together, our data affirm the nucleophilic properties of the persulfide sulfane sulfur and afford new insights into protein S-sulfhydryl chemistry, which may be exploited in future detection strategies.

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His research focuses on peptide/ protein therapeutics and the development of novel peptide/protein chemistries. Figure 6. Examples of regiospecifically constructing fourdisulfide bonds. A) four disulfide-containing single-chainpeptides and B) four disulfide-containing two-chainpeptides.

The oxidation of cysteine thiol side chains by hydrogen peroxide to afford protein sulfenyl modifications is an important mechanism in signal transduction. In addition, aberrant protein sulfenylation contributes to a range of human pathologies, including cancer. Efforts to elucidate the roles of protein sulfenylation in physiology and disease have been hampered by the lack of techniques to probe these modifications in native environments with molecular specificity. In this review, we trace the history of chemical and biological methods that have been developed to detect protein sulfenylation and illustrate how a recent cell-permeable chemical reporter, DYn-2, has been used to detect identify intracellular targets of endogenous H2O2 during growth factor signaling, including the EGF receptor. The array of new tools and methods discussed herein enables the discovery of new biological roles for cysteine sulfenylation in human health and disease.

ObjectiveTo signal, FGF19 and FGF21 require co-receptor βKlotho (KLB) to act in concert with FGF receptors, and yet there is appreciable variance in the C-terminal sequences of these two novel metabolic hormones where binding is believed to be primary. We seek to determine the functional consequences for these amino acid differences and determine whether such information can be used to design high potency antagonists and agonists.MethodsWe employed a functional in vitro assay to identify C-terminal protein fragments capable of fully blocking KLB-mediated FGF19 and 21 receptor signaling. The key residues in each hormone responsible for support full bioactivity were identified through peptide-based Ala-scanning. Chemical optimization of the peptides was employed to increase their antagonistic potency. An optimized sequence as a substituted part of a full length FGF21 was assessed for enhanced FGFR/KLB-mediated agonism using tissue culture and obese mice.ResultsC-terminal FGF19 and FGF21 peptides of relatively short length were observed to potently inhibit the activity of these two hormones, in vitro and in vivo. These FGFs of different sequence also demonstrated a striking conservation of structural determinants to maintain KLB binding. A single C-terminal amino acid in FGF19 was observed to modulate relative activity through FGFR1 and FGFR4. The substitution of native FGF21 C-terminal sequence with a peptide optimized for the highest antagonistic activity resulted in significantly enhanced FGF potency, as measured by in vitro signaling and improvements in metabolic outcomes in diet-induced obese mice.ConclusionsWe report here the ability of short C-terminal peptides to bind KLB and function as antagonists of FGF19 and 21 actions. These proteins maintain high conservation of sequence in those residues central to KLB binding. An FGF21 chimeric protein possessing an optimized C-terminal sequence proved to be a super-agonist in delivery of beneficial metabolic effects in obese mice.

The all‐inorganic CsPbI2Br perovskite with superior thermal durability faces challenges of low‐phase stability and high moisture sensitivity. Herein, a nonionic additive of polyethyleneimine (PEI) with multiple amino groups is introduced to form hydrogen bond with I−/Br− ions and coordinate with Pb2+/Cs+ ions simultaneously. The strong interplay between PEI and CsPbI2Br achieves a well‐controlled grain size, reduced defects, and reinforced phase structure of CsPbI2Br film, which boosts the power conversion efficiency (PCE) of perovskite solar cells to 15.48%. The hydrophobic long alkyl chain of PEI greatly improves the humidity resistance, retaining 81.9% of initial PCE of zjr unsealed device under 20 ± 5% relative humidity (RH) for 500 h. Remarkably, a PCE of 13.37% is achieved by the device based on CsPbI2Br–PEI film processed under ambient condition (≈22% RH, ≈25 °C).