Biology subjects

Ravi, R.

Publications and source records attributed to Ravi, R..

3 recordsLinked to original sources

bioRxiv2020

Production and analysis of a mammalian septin hetero-octamer complex

The septins are filament-forming proteins found in diverse eukaryotes from fungi to vertebrates, with roles in cytokinesis, shaping of membranes and modifying cytoskeletal organization. These GTPases assemble into rod-shaped soluble hetero-hexamers and hetero-octamers in mammals, which polymerize into filaments and higher order structures. While the cell biology and pathobiology of septins are advancing rapidly, mechanistic study of the mammalian septins is limited by a lack of recombinant hetero-octamer materials. We describe here the production and characterization of a recombinant mammalian septin hetero-octamer of defined stoichiometry, the SEPT2/SEPT6/SEPT7/SEPT3 complex. Using a fluorescent protein fusion to the complex, we observed filaments assembled from this complex. In addition, we used this novel tool to resolve recent questions regarding the organization of the soluble septin complex. Biochemical characterization of a SEPT3 truncation that disrupts SEPT3-SEPT3 interactions is consistent with SEPT3 occupying a central position in the complex while the SEPT2 subunits are at the ends of the rod-shaped octameric complexes. Consistent with SEPT2 being on the complex ends, we find that our purified SEPT2/SEPT6/SEPT7/SEPT3 hetero-octamer copolymerizes into mixed filaments with separately purified SEPT2/SEPT6/SEPT7 hetero-hexamer. We expect this new recombinant production approach to lay essential groundwork for future studies into mammalian septin mechanism and function.

biochemistry↗

bioRxiv2020

Impact of glycan positioning on HIV-1 Env glycan shield density, function, and antibody recognition

N-glycans, which represent >50% mass of the HIV-1 envelope (Env) trimer, play important roles for virus-cell entry and immune evasion. How each glycan unit interacts to shape the Env protein-sugar complex and affects Env function is not well understood. Here, high-resolution glycomics analysis of two Env variants from the same donor, with differing functional characteristics and N-glycosylation-site composition, revealed that changes to key N-glycosylation-site not only affected the Env structure at distant locations, but also had a ripple effect on Env-wide glycan processing, virus infectivity, and antibody recognition and virus neutralization. Specifically, the N262 glycan, although not located in the CD4-binding site, controlled Env binding to the CD4 receptor, affected the recognition of Env by several glycan-dependent broadly neutralizing antibodies, and altered heterogeneity of glycosylation at several sites, with N156, N160, and N448 displaying limited glycan processing. Molecular dynamic simulations visualized how specific oligosaccharide positions can move to compensate for loss of a glycan. This study demonstrates how changes in individual glycan units can alter molecular dynamics and processing of the Env-glycan shield and, consequently, Env function.

microbiology↗

bioRxiv2020

Chemical composition and larvicidal activity against Aedes mosquitoes of flower extracts from Clitoria Ternatea

BackgroundMosquito is a human health tread nowadays, the major health problems caused by them are malaria, dengue fever, yellow fever, zika as well as several other outbreaks. The major problem in controlling dengue vectors are the resistant problems. Different classes of insecticides used for public have raised the concern of resistant problem with mosquitoes and environmental pollution. Thus, alternative chemical compounds search is necessary to be searched for overcoming the resistance problem of using pesticides in vectors and the chemical free environment respectively. Thus, to solve these problems, purpose of this study is to identify the larvicidal mechanism, metabolite, antioxidant, chemical compounds and its structure from C. ternatea flower and to test its efficacies against early 4th instar larvae of Ae. aegypti and Ae albopictus. MethodsClitoria ternatea flowers were collected from the Garden of the Faculty of Medicine in International Quest University, Ipoh, Perak and used for crude extraction. Then, the metabolite test, antioxidant test, chromatography techniques were conducted to identify chemical composition of extracts and their chemical structures were identified using GCMS-QP2010 Ultra (Shimadzu). Next, following WHO procedures for larval bioassays, the extracts were used to evaluate against early 4th instar larvae of Aedes mosquito vectors. ResultsThe larvicidal activity of Clitoria ternatea flowers extracts evidently affected the early 4th instar larvae of Aedes mosquito vectors. The highest larvicidal activity was observed against early 4th instar larvae of Ae. aegypti with the LC50 and LC95 values of 1056 and 2491 mg/L, respectively. Meanwhile larvae bioassay test for Ae.albopictus recorded with the LC50 and LC95 values of 1425 and 2753 mg/L. Moreover, the results for non target organism test on Guppy fish, Poecilia reticulate showed no mortalities with flower extracts at 2500 mg/L and posses no toxic effects on fish. In this study, total of 16 chemical compounds and 6 chemical compounds have been reported to posses direct effects on insecticidal, larvicidal and pupicidal effects. Namely 6 chemicals used for insecticidal properties were Glycerin, 2-Hydroxy-gamma-butyrolactone, Neophytadiene, n-Hexadecanoic acid, cis-Vaccenic acid, and Octadecanoic acid with total of 28.7%. Clitoria ternatea flower extracts also showed different types of phenols such as anthocyanin, flavonoid and tannin. ConclusionsOur findings showed that crude extract of Clitoria ternatea flower bioactive molecules to be effective and may be developed as biolarvicides for Aedes mosquito vector control. Furthermore, this study also provided a baseline understanding for future research work on the field applications of Clitoria ternatea flower extracts which could be tested for its long term effects on other non target organisms, including human health.

biochemistry↗