Heparin binding induces conformational changes in Adeno-associated virus serotype 2

Adeno-associated virus serotype 2 (AAV2) uses heparan sulfate proteoglycan as a cell surface-attachment receptor. In this study the structures of AAV2 alone and complexed with heparin were determined to 18 Å resolution using cryo-electron microscopy and three-dimensional image reconstruction. A difference map showed positive density, modeled as heparin, close to the icosahedral twofold axes and between the protrusions that surround the threefold axes of the capsid. Regions of the model near the threefold place the receptor in close proximity to basic residues previously identified as part of the heparin binding site. The region of the model near the twofold axes identifies a second contact site, not previously characterized but which is also possibly configured by heparin binding. The difference map also revealed two significant conformational changes: (I) at the tops of the threefold protrusions, which have become flattened in the complex, and (II) at the fivefold axes where the top of the channel is widened possibly in response to movement of the HI loops in the capsid proteins. Ordered density in the interior of the capsid in the AAV2–heparin complex was interpreted as nucleic acid, consistent with the presence of non-viral DNA in the expressed capsids.     

Understanding the Molecular Dynamics of Type-2 Diabetes Drug Target DPP-4 and its Interaction with Sitagliptin and Inhibitor Diprotin-A

The occurrence of type 2 diabetes (T2D) accounts for 90–95 % of all diabetes. Intestine hormone glucagon-like peptide-1 (GLP-1) has an antidiabetic role that enhances insulin secretion and pancreatic β-cell proliferation. GLP-1 is degraded by the enzyme dipeptidyl peptidase-4 (DPP-4) rapidly. Hence, the DPP-4 inhibition has been preferred not only for the treatment but also as a major drug target. Sitagliptin and Diprotin-A are antihyperglycemic agents for the treatment of T2D. However, little is known on the molecular dynamics of DPP-4 and the interaction properties with its ligands, namely Sitagliptin and Diprotin-A. This study has used the latest bioinformatic tools to understand the molecular dynamics and its interaction properties of DPP-4. This study has explored the number of α helices, β strands, β hairpins, Ψ loop, β bulges, β turns, and ? turns and they were 19, 46, 25, 1, 14, 70, and 4, respectively. The highest number of H-bonds was recorded in α helix of domain-1, and the lowest number H-bonds were noted in α helix of domain-2. During interaction between residues, in A- and B-chain, 47 and 48 residues are involved for interaction, and interaction interface area was more in A-Chain (2176 Å²). From DPP-4 and Sitagliptin interaction, three residues in active sites such as Try226, Glu205, and Glu206 were involved in three H-bond formation, while 10 other amino acids (Try547, Try667, Asn710, Val711, His740, Ser630, Ser209, Arg358, Phe357, and Val207) were involved in hydrophobic interactions. In this review, we have shown the importance of bioinformatics as an excellent tool for a rapid method to assess the molecular dynamics and its interaction properties of DPP-4. Our predictions highlighted in this review will help researchers to understand the interaction properties and recognition of interactive sites to design more DPP-4 inhibitors for the treatment of T2D and drug discovery.     

Antibacterial activity of metabolite produced by Paenibacillus polymyxa strain HKA-15 against Xanthomonas campestris pv. phaseoli

An antibacterial metabolite extracted from Paenibacillus polymyxa HKA-15 showed strong inhibition against Xanthomonas campestris pv. phaseoli strains CP-1-1 and M-5. Minimum inhibitory concentration (MIC) of crude extract against strains CP-1-1 and M-5 was found to be 1.7 mg/ml and 1.52 mg/ml, respectively. In UV-Vis range, the absorption peak of crude extract was maximum at 240 nm. The compound is resilience to wide range of temperature, pH, surfactants and organic solvents. The complete loss of activity was observed when crude metabolite was treated with pepsin (400 unit/ml). Characterization of crude metabolite suggested its hydrophobic and peptide nature. Inhibition of Xanthomonas campestris pv. phaseoli by peptide like metabolite produced by Paenibacillus polymyxa strain HKA-15 under in vitro conditions showed ecological and biotechnological potential of strain HKA-15 to control common blight disease in beans.     

Human carbonic anhydrase III: structural and kinetic study of catalysis and proton transfer

The residue phenylalanine 198 (Phe 198) is a prominent cause of the lower activity of human carbonic anhydrase III (HCA III) compared with HCA II and other isozymes which have leucine at this site. We report the crystal structures of HCA III and the site-directed mutant F198L HCA III, both at 2.1 A resolution, and the enhancement of catalytic activity by exogenous proton donors containing imidazole rings. Both enzymes had a hexahistidine extension at the carboxy-terminal end, used to aid in purification, that was ordered in the crystal structures bound in the active site cavity of an adjacent symmetry-related enzyme. This observation allowed us to comment on a number of possible binding sites for imidazole and derivatives as exogenous proton donors/acceptors in catalysis by HCA III. Kinetic and structural evidence indicates that the phenyl side chain of Phe 198 in HCA III, about 5 A from the zinc, is a steric constriction in the active site, may cause altered interactions at the zinc-bound solvent, and is a binding site for the activation of catalysis by histidylhistidine. This suggests that sites of activation of the proton-transfer pathway in carbonic anhydrase are closer to the zinc than considered in previous studies.     

A special report on India's biotech scenario: Advancement in biopharmaceutical and health care sectors

India's biotechnology industry has been growing towards new heights in conjunction with the recent economic outburst. The country has the potential to revolutionize biopharmaceutical and healthcare sectors. In this review, we have highlighted the achievements of India's biotechnology industry, especially biopharmaceutical and healthcare sectors that include therapeutics, diagnostics, stem cell research, human healthcare related bioinformatics and animal health care. We have also described regulatory mechanisms involved in India's health care biotech including manpower development.     

Structural insights and functional implications of choline acetyltransferase

The biosynthetic enzyme for the neurotransmitter acetylcholine, choline acetyltransferase (ChAT) (E.C. 2.3.1.6), is essential for the development and neuronal activities of cholinergic systems involved in many fundamental brain functions. ChAT catalyzes the transfer of an acetyl group from acetyl-coenzyme A to choline to form the neurotransmitter acetylcholine. Since its discovery more than 60 years ago much research has been devoted to the kinetic studies of this enzyme. For the first time we report the crystal structure of rat ChAT (rChAT) to 1.55 A resolution. The structure of rChAT is a monomer and consists of two domains with an interfacial active site tunnel. This structure, with the modeled substrate binding, provides critical insights into the molecular basis for the production of acetylcholine and may further our understanding of disease causing mutations.