cysteine residue

N-Ethylmaleimide (NEM) is a reagent for alkylation of free sulfhydryl groups, a cysteine protease inhibitor used in experimental biochemistry. N-Ethylmaleimide is also a deubiquitinating enzyme inhibitor that specifically inhibits phosphate transport in mitochondria.

CL2A-SN-38 is a drug-linker conjugate composed of a potent a DNA Topoisomerase I inhibitor SN-38 and a linker CL2A to make antibody drug conjugate (ADC).. CL2A-SN-38 is composed of a potent a DNA Topoisomerase I inhibitor SN-38 and a linker CL2A to make antibody drug conjugate (ADC). CL2A-SN-38 provides significant and specific antitumor effects against a range of human solid tumor types. CL2A is a noncleavable complicated PEG8- and triazole-containing PABC-peptide-mc linker. CL2A is cleavable through pH sensitivity, giving rise to bystander effect, and binds the antibody at a cysteine residue via a disulfide bond. .

MS8511, a selective covalent irreversible inhibitor of G9a/GLP, targets a cysteine residue at the substrate binding site, displaying IC50 values of 100 nM (G9a) and 140 nM (GLP), alongside Kd values of 44 nM (G9a) and 46 nM (GLP). This compound effectively reduces cellular H3K9me2 levels and boosts antiproliferation activity, making it applicable in cancer research involving brain, breast, ovarian, lung, bladder, melanoma, and colorectal cancers, as well as studies on Alzheimer’s disease (AD), sickle cell disease, and Prader−Willi syndrome (PWS) [1].

Leptomycin B (LMB) is a potent inhibitor of the nuclear export of proteins and is a potent antifungal antibiotic blocking the eukaryotic cell cycle. Leptomycin B inactivates CRM1/exportin 1 by covalent modification at a cysteine residue.

Melittin (C-term cysteine labeled), a variant of the toxic bee venom peptide melittin featuring a cysteine residue at its C-terminus, effectively induces hemolysis in isolated human red blood cells at both endosomal and extracellular pH levels, with EC50 values of 5 µM at pH 5.5 and 6 µM at pH 7.4. This compound is utilized in creating membrane-lytic polymers for the synthesis of polyplexes, facilitating plasmid delivery both in vitro and in vivo.

Peptide M is a synthetic Peptide, 50 aa, derived from streptococcus M protein, containing an additional c-terminal cysteine residue.

2'-Thioadenosine (PD157432) serves as a selective and irreversible inhibitor of ErbB-1 and ErbB-2 tyrosine kinases, demonstrating an IC50 value of 45 µM against ErbB-2. It achieves covalent inactivation of ErbB-1 through modification of a cysteine residue within the enzyme's active site [1].

AM841, a high-affinity electrophilic ligand, covalently interacts with a cysteine residue in helix six, thus activating the CB1 cannabinoid receptor. It diminishes forskolin-stimulated cAMP accumulation and slows gastrointestinal motility [1] [2].

Human α-Defensin 6, a 32-residue, cysteine-rich peptide, plays a crucial role in mucosal immunity by inhibiting bacterial invasion through the formation of ordered self-assembly fibrils and nanonets, which bind to bacterial surface proteins and entangle the bacteria. Additionally, Human α-Defensin 6 impedes biofilm formation by C. albicans [1] [2].

Poseltinib is an orally active, selective, and irreversible Bruton's tyrosine kinase (BTK) inhibitor, exhibiting a half-maximal inhibitory concentration (IC 50) of 1.95 nM. It demonstrates 0.3, 2.3, and 2.4-fold greater selectivity for BTK over BMX, TEC, and TXK, respectively. This compound covalently binds to BTK's active site at the cysteine 481 residue, effectively inhibiting signaling pathways mediated by the B cell receptor (BCR), Fc receptor (FcR), and Toll-like receptor (TLR).

FLAG-Cys is a Flag peptide modified with an additional cysteine (Cys) residue, recognized for its immunogenicity [1].

CL2A is a pH-sensitive, cleavable PEG8- and triazole-containing PABC-peptide-mc linker, characterized by its ability to induce a bystander effect. It forms a disulfide bond with an antibody at a cysteine residue. Labetuzumab govitecan utilizes this linker for its drug conjugation[1].

Epsilon-V1-2, a Cys-conjugated, is a biologically active peptide known as the εPKC-specific inhibitor. It hampers εPKC functionality by obstructing its translocation and the phosphorylation of MARCKS, additionally perturbing εPKC's interaction with its anchoring protein, εRACK. The peptide includes a cysteine residue at its C-terminus, facilitating the formation of potential disulfide bonds with carrier proteins. Pyroglutamyl formation can occur spontaneously at the N-terminus if glutamine or glutamic acid is present, enhancing peptide stability against gastrointestinal proteases. Pyroglutamyl peptides, a recognized subset, are accounted for in the peptide's purity during HPLC analysis.

Olmutinib is a novel third-generation epidermal growth factor receptor (EGFR) mutation-specific tyrosine kinase inhibitor, used in the treatment of T790M mutation positive non-small cell lung cancer. Olmutinib covalently binds a cysteine residue near the kinase domain of mutant EGFRs to prevent phosphorylation of the receptor. EGFRs are frequently over-expressed in lung cancer and contribute to activation of the phosphoinositide 3-kinase and mitogen-activated protein kinase pathways which both promote cell survival and proliferation. By inhibiting EGFR activation, Olmutinib attenuates the activation of these tumor-promoting pathways. In the first phase I/II clinical study of Osimertinib, 800 mg/ day was chosen as the dose for subsequent studies, and the dose-limiting toxicity and maximum tolerated dose was not reached. Olmutinib received breakthrough therapy designation in the United States in December 2015 and was approved for use in Korea in May 2016.

Cys(Npys)-TAT (47-57), a peptide fragment corresponding to the transduction domain of the TAT peptide, contains an activated cysteine residue C and can electrostatically interact with plasmid DNA. Notably, TAT is a small nuclear transcriptional activator protein encoded by HIV-1 [1].