Modification of N-terminal α-amine of proteins via biomimetic ortho-quinone-mediated oxidation

Abstract

Naturally abundant quinones are important molecules, which play essential roles in various biological processes due to their reduction potential. In contrast to their universality, the investigation of reactions between quinones and proteins remains sparse. Herein, we report the development of a convenient strategy to protein modification via a biomimetic quinone-mediated oxidation at the N-terminus. By exploiting unique reactivity of an ortho-quinone reagent, the α-amine of protein N-terminus is oxidized to generate aldo or keto handle for orthogonal conjugation. The applications have been demonstrated using a range of proteins, including myoglobin, ubiquitin and small ubiquitin-related modifier 2 (SUMO2). The effect of this method is further highlighted via the preparation of a series of 17 macrophage inflammatory protein 1β (MIP-1β) analogs, followed by preliminary anti-HIV activity and cell viability assays, respectively. This method offers an efficient and complementary approach to existing strategies for N-terminal modification of proteins.

Insight into the Antibacterial Activity of Selected Metal Nanoparticles and Alterations within the Antioxidant Defence System in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis

“…This is in accordance with high LPO levels in these bacteria as well as significant changes in CAT, PER, SOD and DEH activities. Moreover, further oxidation of protein side chains containing amine groups can also result in considerable changes in their overall content because these groups amongst sulphurcontaining ones are the most susceptible to oxidative changes forced by ROS [58,60]. Here, it was also established that ZnO-NPs was characterised by the strongest stimulating effect on -NH 2 content in bacterial cells.…”

“…The principal of the >C=O content assay is based on the reaction of protein carbonyl groups with 2,4dinitrophenylhydrazine (DNPH), resulting in the formation of 2,4-dinitrophenylhydrazones measured calorimetrically [53,80,81]. Subsequently, -NH 2 content measurement is based on the reaction of fluorescamine with amine groups, which produces fluorescent product proportional to the amine content in a sample, whilst the unbound fluorescamine hydrolyses to non-fluorescent products [60,81]. The supernatant for analysis was obtained in a similar way to the procedure for isolating antioxidant enzymes.…”

Self-Adjuvanting Lipoprotein Conjugate αGalCer-RBD Induces Potent Immunity against SARS-CoV-2 and its Variants of Concern

“…To evaluate the yield of the conjugation reaction, an RBD protein 319/321 fragment containing an Arg residue at its N -terminus was synthesized as a model tripeptide to conjugate with O-ethylhydroxylamine hydrochloride ( Scheme S1 ). 49 The results of HPLC and ESI-MS analysis indicated a >95% overall yield of the conjugation reaction ( Figure S1 ). Besides, the RBD protein was modified with a fluorescent biolabeling molecule, rhodamine B (RhB), on the N -terminus using PLP-mediated transamination ( Scheme S2 ).…”

An overview of chemo- and site-selectivity aspects in the chemical conjugation of proteins

“…Numerous reports about general strategies for the chemo- and site-selective modification of α-amino groups of native proteins can already be found, including in the recent literature [ 229 ]. Most of these methods employ carbonyls, and aromatic aldehydes in particular, but sulfonamides, phthalimides or enzymes were also demonstrated to be valuable candidates for this job.…”