Interface Interactions of the Bowman-Birk Inhibitor BTCI in a Ternary Complex with Trypsin and Chymotrypsin Evaluated by Semiempirical Quantum Mechanical Calculations: Interface Interactions of the Bowman-Birk Inhibitor BTCI in a Ternary Complex with Trypsin and Chymotrypsin Evaluated by Semiempirical Quantum Mechani

Development of a rapid process for purification of Bowman-Birk and Kunitz inhibitors from legume seeds, and evaluation of their biophysical, insecticidal, and antimicrobial properties

Bowman-Birk inhibitor (BBI ~10 kDa) and Kunitz inhibitor (KI ~20 kDa) are serine protease/proteinase inhibitor(s) [PI(s)] ubiquitously found in several Leguminous plant species with insecticidal and therapeutic properties. Due to narrow molecular mass differences, the separation of these inhibitors from a single seed variety is tedious. The present study is aimed to develop a rapid protocol (<24 h) for purifying BBI and KI from legume seeds using mild trichloroacetic acid (TCA) extraction followed by trypsin-affinity chromatography. The mature seeds of Vigna radiata and Cajanus platycarpus are used as a model to purify BBI and KI using this protocol. The BBI and KI purified from the seeds of V. radiata are labeled as VrBBI & VrKI, and C. platycarpus are labeled as CpBBI & CpKI, respectively. These PIs are confirmed by immunodetection and MALDI-TOF studies and further characterized for their structural (CD & fluorescence spectroscopy) and functional properties (temperature & DTT stability). BBI(s) purified using the above process are effective in the management of castor semi-looper 'Achaea janata', while KI(s) are effective in the management of pod borer 'Helicoverpa armigera'. Besides, both BBI(s) and KI(s) have significant potential in controlling the growth of methicillin-sensitive 'Staphylococcus aureus', a gram-positive pathogenic bacterium.

Electronic and structural study of T315I mutated form in DFG-out conformation of BCR-ABL inhibitors

In this work, the four main drugs for the treatment of chronic myeloid leukemia were analyzed, being imatinib, dasatinib, nilotinib and ponatinib followed by four derivative molecules of nilotinib and ponatinib. For these derivative molecules, the fluorine atoms were replaced by hydrogen and chlorine atoms in order to shade light to the structural effects on this set of inhibitors. Electronic studies were performed at density functional theory level with the B3LYP functional and 6-311+G(d,p) basis set. The frontier molecular orbitals, gap HOMO-LUMO, and NBO were analyzed and compared to docking studies for mutant T315I tyrosine kinase protein structure code 3IK3, in the DFG-out conformation. Structural similarities were pointed out, such as the presence of groups common to all inhibitors and modifications raised up on new generations of imatinib-based inhibitors. One of them is the trifluoromethyl group present in nilotinib and later included in ponatinib, in addition to the 1-methylpiperazin-1-ium group that is present in imatinib and ponatinib. The frontier molecular orbitals of imatinib and ponatinib are contributing to the same amino acid residues, and the ineffectiveness of imatinib against the T315I mutation was discussed.Communicated by Ramaswamy H. Sarma.

Bowman-Birk Inhibitors: Insights into Family of Multifunctional Proteins and Peptides with Potential Therapeutical Applications

Bowman-Birk inhibitors (BBIs) are found primarily in seeds of legumes and in cereal grains. These canonical inhibitors share a highly conserved nine-amino acids binding loop motif CTP1SXPPXC (where P1 is the inhibitory active site, while X stands for various amino acids). They are natural controllers of plants' endogenous proteases, but they are also inhibitors of exogenous proteases present in microbials and insects. They are considered as plants' protective agents, as their elevated levels are observed during injury, presence of pathogens, or abiotic stress, i.a. Similar properties are observed for peptides isolated from amphibians' skin containing 11-amino acids disulfide-bridged loop CWTP1SXPPXPC. They are classified as Bowman-Birk like trypsin inhibitors (BBLTIs). These inhibitors are resistant to proteolysis and not toxic, and they are reported to be beneficial in the treatment of various pathological states. In this review, we summarize up-to-date research results regarding BBIs' and BBLTIs' inhibitory activity, immunomodulatory and anti-inflammatory activity, antimicrobial and insecticidal strength, as well as chemopreventive properties.

Blood pressure-lowering effects of a Bowman-Birk inhibitor and its derived peptides in normotensive and hypertensive rats

Bioactive plant peptides have received considerable interest as potential antihypertensive agents with potentially fewer side effects than antihypertensive drugs. Here, the blood pressure-lowering effects of the Bowman-Birk protease inhibitor, BTCI, and its derived peptides, PepChy and PepTry, were investigated using normotensive (Wistar-WR) and spontaneously hypertensive rats (SHR). BTCI inhibited the proteases trypsin and chymotrypsin, respectively, at 6 µM and 40 µM, a 10-fold greater inhibition than observed with PepTry (60 µM) and PepChy (400 µM). These molecules also inhibited angiotensin converting enzyme (ACE) with IC50 values of 54.6 ± 2.9; 24.7 ± 1.1; and 24.4 ± 1.1 µM, respectively, occluding its catalytic site, as indicated by molecular docking simulation, mainly for PepChy and PepTry. Gavage administration of BTCI and the peptides promoted a decrease of systolic and diastolic blood pressure and an increase of renal and aortic vascular conductance. These effects were more expressive in SHR than in WR. Additionally, BTCI, PepChy and PepTry promoted coronary vasodilation and negative inotropic effects in isolated perfused hearts. The nitric oxide synthase inhibitor blunted the BTCI and PepChy, with no cardiac effects on PepTry. The findings of this study indicate a therapeutic potential of BTCI and its related peptides in the treatment of hypertension.

SQM/COSMO Scoring Function: Reliable Quantum-Mechanical Tool for Sampling and Ranking in Structure-Based Drug Design

Quantum mechanical (QM) methods have been gaining importance in structure-based drug design where a reliable description of protein-ligand interactions is of utmost significance. However, strategies i. e. QM/MM, fragmentation or semiempirical (SQM) methods had to be pursued to overcome the unfavorable scaling of QM methods. Various SQM-based approaches have significantly contributed to the accuracy of docking and improvement of lead compounds. Parametrizations of SQM and implicit solvent methods in our laboratory have been instrumental to obtain a reliable SQM-based scoring function. The experience gained in its application for activity ranking of ligands binding to tens of protein targets resulted in setting up a faster SQM/COSMO scoring approach, which outperforms standard scoring methods in native pose identification for two dozen protein targets with ten thousand poses. Recently, SQM/COSMO was effectively applied in a proof-of-concept study of enrichment in virtual screening. Due to its superior performance, feasibility and chemical generality, we propose the SQM/COSMO approach as an efficient tool in structure-based drug design.