The plant genome contains a large number of sequences that encode catalytically inactive chitinases referred to as chitinase-like proteins (CLPs). Although CLPs share high sequence and structural homology with chitinases of glycosyl hydrolase 18 (TIM barrel domain) and 19 families, they may lack the binding/catalytic activity. Molecular genetic analysis revealed that gene duplication events followed by mutation in the existing chitinase gene have resulted in the loss of activity. The evidences show that adaptive functional diversification of the CLPs has been achieved through alterations in the flexible regions than in the rigid structural elements. The CLPs plays an important role in the defense response against pathogenic attack, biotic and abiotic stress. They are also involved in the growth and developmental processes of plants. Since the physiological roles of CLPs are similar to chitinase, such mutations have led to plurifunctional enzymes. The biochemical and structural characterization of the CLPs is essential for understanding their roles and to develop potential utility in biotechnological industries. This review sheds light on the structure-function evolution of CLPs from chitinases.

The crystal structure of chikungunya (CHIKV) virus capsid protease domain has been determined at 2.2Å. Structure reveals a chymotrypsin-like protease fold with a conserved hydrophobic pocket in CHIKV capsid protein (CP) for interaction with the cytoplasmic tail of E2 (cdE2) similar to the capsid protein of other alphaviruses. Molecular contacts between CP-cdE2 were determined by fitting structures of CHIKV CP and cdE2 into the cryo-EM map of Venezuelan equine encephalitis virus (VEEV). Binding of (S)-(+)-Mandelic acid (MDA) and Ethyl 3-aminobenzoate (EAB) to the hydrophobic pocket of CP was evaluated by molecular docking. Surface plasmon resonance (SPR) and fluorescence spectroscopy experiments confirmed MDA and EAB binding to the CP. The binding constants (K) obtained from SPR for MDA and EAB were 1.2 × 10 M and 0.2 × 10 M, respectively. This study adds to the understanding of chikungunya virus structural proteins and may serve as the basis for antiviral development against chikungunya disease.

No abstract

Globulins are a major class of seed storage proteins which were thought to be enzymatically inactive. These proteins belong to the most ancient cupin superfamily. They can be graded into 11S legumin type and 7S vicilin type based on their sedimentation coefficients. Members from both classes share structural homology are thought to have evolved from either one-domain germin predecessor by duplication or by horizontal gene transfer of two-domain gene from bacteria to eukaryotes. Globulins are known to define the nutritional quality of the seeds, however, they are also involved in sucrose binding, desiccation, defense against microbes, hormone binding and oxidative stress etc. Major drawback with globulins is their tendency to bind to IgE. Studying structural-functional behavior of such protein can help in modifying proteins for enhanced functionality in food processing industries.

Momordica charantia (Mc) seeds are widely used edible crop with high nutritional quality. The food and pharmaceutical industries use it as a natural anti-oxygenic agent. Herein, a ~52 kDa protein, which is a major part of seed proteome has been purified, biochemically characterized and structure has been determined. MALDI-ESI-MS identified peptide fragments and contig-deduced sequence suggested the protein to be homologous to 7S globulins. The crystal structure shows that protein has a bicupin fold similar to 7S globulins and the electron density for a copper and acetate ligand were observed in the C-terminal barrel domain. In silico study reveals that a tripeptide (VFK) from Mc7S possess a higher binding affinity for angiotensin converting enzyme (ACE) than already reported drug Lisinopril (LPR). The protein is a glycoprotein and highly stable under varying thermal and pH conditions due to its secondary structures. The DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay showed the protein to have an anti-oxygenic nature and can aid in scavenging free radical from sample. The protein can assist to enhance the nutritional and functional value of food by acting as a food antioxidant. Further, characterization of Mc7S required which might add in importance of Mc7S as antioxidant, anti-diabetic and anti-hypertensive. Momordica charantia (Mc) commonly known as bitter melon or bitter gourd is a member of Cucurbitaceae family, which grows in tropical and subtropical areas. The plant is known for centuries in Ayurveda for its anti-bacterial, anti-fungal, anti-viral, anti-parasitic, hypoglycemic, anti-fertility, anti-tumorous, and anti-carcinogenic properties 1-5. It is preferred as a medication for a broad range of health applications, including the treatment of dysmenorrhea, eczema, emmenagogue, galactagogue, gout, jaundice, kidney (stone), leprosy, leucorrhea, piles, pneumonia, psoriasis, rheumatism, scabies, T2DM (type 2 diabetes mellitus), obesity, hypertension, bacterial and viral infections, cancer, and even AIDS 1-5. It contains biologically active molecules including proteins, triterpenes, saponins, steroids, flavonoids, alkaloids, and acids 6. Each part of plant i.e. seeds, roots, leaves and especially unripe fruits has its pharmacological properties 4. The juice is used to cure a large number of conditions such as for articular pain relief and chronic fever in jaundice, liver disease, and digestive system diseases because of laxative, diuretic, and anti-helminthic effects. In the case of chronic skin diseases, it is applied locally to treat boils, burns, and rash. Moreover, components of Mc plant i.e. unripe fruit, seeds and aerial parts are largely known for its anti-diabetic properties due to the presence of insulin-mimetic in the seeds 7,8. The aqueous seed extract of Mc also scavenges the free radicals for protection against lipid peroxidation thereby reducing the risk of diabetic complications 9. The strong anti-oxygenic activity may be due to the presence of phenolic compounds and saponins 10. The globula...