RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY

The three-dimensional structure of the antigen-binding fragment (Fab) of the monoclonal antibody LNKB-2 in complex with the synthetic antigenic nonapeptide of human interleukin-2 (IL-2; Lys-Pro-Leu-Glu-Glu-Val-Leu-Asn-Leu-O) was determined by X-ray method at a resolution of 2.6 Å in crystal space group P2₁2₁2₁. The peptide adopts a somewhat distorted α-helical conformation, close to that of fragment 64–72 of the IL-2 antigen. Four out of the six hypervariable loops in the antigen-binding site of the Fab fragment are involved in nonapeptide association through hydrogen bonding, salt bridge formation, and hydrophobic interactions. Moreover, Tyr residues of an antibody play an important role in antigen-antibody recognition.

In screening the venoms of various snake species, we found that the venom of the Madagascar cat-eyed snake Madagascarophis colubrinus competes with α-bungarotoxin for binding to the nicotinic acetylcholine receptor from Torpedo californica. Using liquid chromatography, a peptide, called macoluxin and inhibiting the binding of the toxin to the receptor, was isolated from the venom. The amino acid sequence of this 23-amino acid peptide was determined by automatic Edman degradation. Comparison with amino acid sequences of known proteins showed that the macoluxin sequence is homologous to the α-helical region of the sequence of snake venom metalloproteinases. The peptide was synthesized by solid-phase peptide synthesis, and the study of its biological activity showed that it inhibits the binding of α-bungarotoxin to the Torpedo receptor with an IC₅₀ of 47 μM. Macoluxin also reversibly inhibited acetylcholine-induced currents in the muscle-type nicotinic acetylcholine receptor. This is the first data on the presence in the venom of rear fanged snakes of a peptide that can inhibit the nicotinic acetylcholine receptor.

An efficient system for the biosynthesis, isolation and purification of recombinant human neuroglobin has been developed and optimized, which makes it possible to produce protein in quantities sufficient to study its properties. According to UV-visible, IR-, CD-, and NMR spectroscopy data, recombinant neuroglobin is a structured protein in the holoform state. The data of chromato-mass-spectrometric analysis made it possible to conclude that there is a correctly formed disulfide bond in the structure of the oxidized form of the protein. Using Raman and surface-enhanced Raman spectroscopy with laser excitation at 532 nm, it was shown that heme in the reduced and oxidized forms of neuroglobin has vibrational degrees of freedom typical of b-type hemes, and the iron atom is six-coordinated. Using Raman spectroscopy with laser excitation at 633 nm, it was found that reduced –SH-groups were present in reduced neuroglobin, while in oxidized neuroglobin disulfide bridge was formed. The results obtained serve as the basis for detailed studies of the mechanism of the functioning of neuroglobin as a neuroprotector, in particular, during its interaction with oxidized cytochrome c, which is released from mitochondria in violation of their functioning and/or morphology.

In the 1960s and 1970s, the Institute of Chemistry of Natural Compounds developed a topochemical approach for designing new biologically active peptide compounds, the applicability of which to the creation of inhibitors and effective substrates of proteolytic enzymes was shown by the author of this review under the direct supervision of V.T. Ivanov. The next task was to establish the conformation of protein neurotoxins from snake venoms and to study the topography of their binding to the target, the nicotinic acetylcholine receptor (nAChR) from the electric organ of the Torpedo marmorata ray. With selectively labeled derivatives containing one fluorescent or spin label on established amino acid residues, neurotoxin residues in contact with nAChR were identified for the first time. Later, in collaboration with the laboratory of V.T. Ivanov, new analogues of α-conotoxins (peptide neurotoxins from poisonous mollusks Conus), were synthesized including their photoactivated derivatives, which showed the participation of all Torpedo nAChR subunits in the binding of α‑conotoxins. The final part of the review briefly presents the recent achievements of the Department of Molecular Neuroimmune Signaling (headed by V.I. Tsetlin) concerning the isolation and synthesis of new peptide and protein neurotoxins and the study of their mechanism of action.

In the era of the growing global threat of antibiotic resistance, antimicrobial peptides (AMPs) are considered as new generation drugs for treatment of various infectious diseases. In this review, AMPs are seen as an alternative to traditional antibiotics, many of which have already lost or are gradually reducing their effectiveness against a number of critically important pathogenic microorganisms. Recent outbreaks of secondary infections during the COVID-19 pandemic have increased the interest in AMPs due to an acute shortage of effective agents against bacterial and fungal infections. The review summarized current data on clinical studies of AMPs, assembled a list of developed drugs based on AMPs at various stages of clinical trials, highlighted the urgency of study of new AMPs, and systematized the most relevant clinical data and application of AMPs.