Biology subjects

Bhadra, P.

Publications and source records attributed to Bhadra, P..

3 recordsLinked to original sources

bioRxiv2026

De-Novo Designed Antibacterial N95 Facial Mask: Comprising a Nano-Garden Using ZnO Nanoflower

Nowadays N95 facial mask has gain huge attention due to COVID19 pandemic situation and it serves as the prime PPE. Though the microbes can be restricted to get inside the human body due to the presence of mask temporarily, but over the time, bacteria and other microbes may get entrapped into the threads of the mask itself and thus acting as a storage chamber of microbes. It is necessary to eliminate them from the mask surface. To do so different floral structured Nano-ZnO with variable oriented arrangement of petals were fabricated on the surface of the N95 mask and further characterized through instrumentations including XRD, FTIR,UV-Vis, Fluorescence-Spectroscopy, SEM, DLS. The average crystallite size calculated for synthesized four different ZnO nanoflower were 25.19 nm, 23.46 nm, 27.27 nm and 31.78 nm (for glycerol, PEG, EDTA, Chitosan assisted) respectively. The antimicrobial activity was investigated by standard microbial broth dilution assay and Kirby-Bauer test which assured the inhibition of the bacterial growth. The MIC-MBC value of ZnO nanoflowers for E.coli and B. subtilis were found to be effective at dilution of 250 {micro}g/ml and 100 {micro}g/ml. Additionally a modified Kirby-Bauer assay has been designed to investigate the killing efficiency of the bacteria (E.coli). O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/719592v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@a76030org.highwire.dtl.DTLVardef@9bf1b3org.highwire.dtl.DTLVardef@19232forg.highwire.dtl.DTLVardef@54fe68_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFig. - Graphical AbstractC_FLOATNO C_FIG

microbiology↗

bioRxiv2024

The conserved membrane-proximal domain of Sbh1/ Sec61β guides signal peptides into the Sec61 channel

In eukaryotes, protein secretion begins with protein translocation through the universally conserved Sec61 channel into the endoplasmic reticulum (ER). Its {beta}-subunit, Sbh1 in yeast, enhances ER import of proteins with specific suboptimal signal peptides by an unknown mechanism. The Sbh1 cytosolic N-terminus consists of an intrinsically disordered, non-conserved region (IDR) that has never been visualized in active channel structures, but is close to the translocating polypeptide in the cytosolic channel vestibule. The Sbh1/Sec61{beta} N-terminal IDR is followed by structured 15 amino acids and its C-terminal transmembrane helix, both of which are conserved. We show here that the proline and adjacent conserved residues at the Sbh1 cytosolic/transmembrane domain interface form a hinge that positions the Sbh1 cytosolic domain across the channel vestibule and orients it with respect to the lateral gate. This orientation is critical for Sbh1-dependent protein insertion into the channel. Sbh1-dependence of Sec61 channel insertion is a function of the signal peptide of the respective secretory protein. By chemical crosslinking of purified cytosolic domains of Sbh1 and its paralog Sbh2 to synthetic signal peptides derived from their respective client proteins, we show that the cytosolic domains of Sbh1 and Sbh2 contain specific signal peptide binding sites. The position of the crosslinked residues suggests that signal peptide binding is mediated by the IDRs. We conclude that Sec61{beta} homologs directly recognize signal peptides of their substrates and guide them into the Sec61 channel; they thus control entry of specific proteins into the secretory pathway.

biochemistry↗

bioRxiv2021

Mycolactone enhances the Ca2+ leakage from endoplasmic reticulum by trapping Sec61 translocons in a Ca2+ permeable state

The Mycobacterium ulcerans exotoxin, mycolactone, is an inhibitor of co-translational translocation via the Sec61 complex. Mycolactone has previously been shown to bind to, and alter the structure of, the major translocon subunit Sec61, and change its interaction with ribosome nascent chain complexes. In addition to its function in protein translocation into the ER, Sec61 also plays a key role in cellular Ca2+ homeostasis, acting as a leak channel between the endoplasmic reticulum (ER) and cytosol. Here, we have analysed the effect of mycolactone on cytosolic and ER Ca2+ levels using compartment-specific sensors. We also used molecular docking analysis to explore potential interaction sites for mycolactone on translocons in various states. These results show that mycolactone enhances the leak of Ca2+ ions via the Sec61 translocon, resulting in a slow but substantial depletion of ER Ca2+. This leak was dependent on mycolactone binding to Sec61 because resistance mutations in this protein completely ablated the increase. Molecular docking supports the existence of a mycolactone-binding transient inhibited state preceding translocation and suggests mycolactone may also bind Sec61 in its idle state. We propose that delayed ribosomal release after translation termination and/or translocon "breathing" during rapid transitions between the idle and intermediate-inhibited states allow for transient Ca2+ leak, and mycolactones stabilisation of the latter underpins the phenotype observed.

biochemistry↗