Toxins for decoding interface selectivity in nicotinic acetylcholine receptors
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that play crucial roles in neurotransmission and regulate complex processes in brain functions, including anxiety, learning and memory, food intake, drug addiction, cognition and nociception. To perform these and other functions, a diverse array of nAChR subtypes are generated by homomeric or heteromeric assembly of 17 homologous nAChR subunits. Agonists, acetylcholine and nicotine, bind to the interface formed between two α subunits and between α and non-α subunits to activate the nAChR and allow cation influx. The divers...
Source: Biochemical Journal - May 27, 2019 Category: Biochemistry Authors: Kini, R. M. Tags: Commentaries Source Type: research
A non-catalytic function of carbonic anhydrase IX contributes to the glycolytic phenotype and pH regulation in human breast cancer cells
The most aggressive and invasive tumor cells often reside in hypoxic microenvironments and rely heavily on rapid anaerobic glycolysis for energy production. This switch from oxidative phosphorylation to glycolysis, along with up-regulation of the glucose transport system, significantly increases the release of lactic acid from cells into the tumor microenvironment. Excess lactate and proton excretion exacerbate extracellular acidification to which cancer cells, but not normal cells, adapt. We have hypothesized that carbonic anhydrases (CAs) play a role in stabilizing both intracellular and extracellular pH to favor cancer ...
Source: Biochemical Journal - May 27, 2019 Category: Biochemistry Authors: Mboge, M. Y., Chen, Z., Khokhar, D., Wolff, A., Ai, L., Heldermon, C. D., Bozdag, M., Carta, F., Supuran, C. T., Brown, K. D., McKenna, R., Frost, C. J., Frost, S. C. Tags: Research Articles Source Type: research
Screening substrate-binding positions by rolling circle amplification suggesting a binding model of Nt.BstNBI
Nicking endonucleases (NEs) become increasingly attractive for their promising applications in isothermal amplification. Unfortunately, in comparison with their applications, their catalytic mechanism studies have relatively lagged behind due to a paucity of crystal structure information. Nt.BstNBI is one of those widely used NEs. However, many aspects of its catalytic mechanism still remained to be explored. Herein, we employed only rolling circle amplification (RCA) assay as a major analytic tool and succeeded in identifying the potential binding positions and regions of the DNA substrate based on locked nucleic acid mod...
Source: Biochemical Journal - May 27, 2019 Category: Biochemistry Authors: Wei, H., Tang, S., Duan, X., Guan, Y., Zhao, G. Tags: Research Articles Source Type: research
Designing active RNF4 monomers by introducing a tryptophan: avidity towards E2~Ub conjugates dictates the activity of ubiquitin RING E3 ligases
Ubiquitin RING E3 ligases (E3s) catalyze ubiquitin (Ub) transfer to their substrates by engaging E2~Ub intermediates with the help of their RING domains. Different E3s have been found to contain a conserved tryptophan residue in their RING that plays an essential role in E2 binding and, hence, enzymatic activity. Many active E3s, however, lack this specific residue. We mined through the existing data to observe that the conservation of the tryptophan and quaternary organization of the RING domains are remarkably correlated. Monomeric RINGs possess the tryptophan while all well-characterized dimeric RINGs, except RNF8, cont...
Source: Biochemical Journal - May 27, 2019 Category: Biochemistry Authors: Sarkar, S., Behera, A. P., Borar, P., Banka, P. A., Datta, A. B. Tags: Research Articles Source Type: research
Discerning the mechanism of action of HtrA4: a serine protease implicated in the cell death pathway
High-temperature requirement protease A4 (HtrA4) is a secretary serine protease whose expression is up-regulated in pre-eclampsia (PE) and hence is a possible biomarker of PE. It has also been altered in cancers such as glioblastoma, breast carcinoma, and prostate cancer making it an emerging therapeutic target. Among the human HtrAs, HtrA4 is the least characterized protease pertaining to both structure and its functions. Although the members of human HtrA family share a significant structural and functional conservation, subtle structural changes have been associated with certain distinct functional requirements. Therefo...
Source: Biochemical Journal - May 20, 2019 Category: Biochemistry Authors: Kummari, R., Dutta, S., Chaganti, L. K., Bose, K. Tags: Research Articles Source Type: research
Multi-functional regulator MapZ controls both positioning and timing of FtsZ polymerization
The tubulin-like GTPase protein FtsZ, which forms a discontinuous cytokinetic ring at mid-cell, is a central player to recruit the division machinery to orchestrate cell division. To guarantee the production of two identical daughter cells, the assembly of FtsZ, namely Z-ring, and its precise positioning should be finely regulated. In Streptococcus pneumoniae, the positioning of Z-ring at the division site is mediated by a bitopic membrane protein MapZ (mid-cell-anchored protein Z) through direct interactions between the intracellular domain (termed MapZ-N (the intracellular domain of MapZ)) and FtsZ. Using nuclear magneti...
Source: Biochemical Journal - May 20, 2019 Category: Biochemistry Authors: Feng, Z., Zhang, J., Xu, D., Jiang, Y.-L., Zhou, C.-Z., Chen, Y. Tags: Research Articles Source Type: research
Phosphatase of regenerating liver sensitizes MET to functional activation by hepatocyte growth factor
In this study, we show that inducible expression of PRL in MDCK normal epithelial cells sensitized MET, the receptor for hepatocyte growth factor (HGF), to functional activation by HGF. We found that PRL expression amplified tyrosine phosphorylation levels of various proteins, among which MET was identified to be the most abundant. This phosphorylation occurred selectively at Y1234/1235 in the activation loop of MET, whereas phosphorylation of Y1349 in the effector-binding site, which is directly involved in downstream signaling, was almost undetectable. Consistently, PRL overexpression by itself did not cause observable a...
Source: Biochemical Journal - May 20, 2019 Category: Biochemistry Authors: Kojima, T., Funato, Y., Miki, H. Tags: Research Articles Source Type: research
An acetylation mimicking mutation, K274Q, in tau imparts neurotoxicity by enhancing tau aggregation and inhibiting tubulin polymerization
In this study, we have examined the molecular mechanism of the toxicity of acetylated K274-tau. We incorporated an acetylation mimicking mutation at K274 (K->Q) residue of tau. The mutation (K274Q) strongly reduced the ability of tau to bind to tubulin and also to polymerize tubulin while K274R mutation did not reduce the ability of tau either to bind or polymerize tubulin. In addition, K274Q-tau displayed a higher aggregation propensity than wild-type tau as evident from thioflavin S fluorescence, tryptophan fluorescence, and electron microscopic images. Furthermore, dynamic light scattering, atomic force microscopy, a...
Source: Biochemical Journal - May 20, 2019 Category: Biochemistry Authors: Rane, J. S., Kumari, A., Panda, D. Tags: Research Articles Source Type: research
Glycolic acid attenuates UVB-induced aquaporin-3, matrix metalloproteinase-9 expression, and collagen degradation in keratinocytes and mouse skin
We reported that GA slows down cell inflammation and aging caused by UVB. Little is known about GA retarding the skin premature senescence or how to impede these events. To investigate the potential of GA to regulate the expression of MMPs and collagen, GA was topically applied onto human keratinocytes and the C57BL/6J mice dorsal skin. In the present study, we demonstrated that GA reduced UVB-induced type-I procollagen expression and secretory collagen levels. GA reverted and dose-dependently increased the level of aquaporin-3 (AQP3), the expression of which was down-regulated by UVB. The UV-induced MMP-9 level and activi...
Source: Biochemical Journal - May 20, 2019 Category: Biochemistry Authors: Tang, S.-C., Tang, L.-C., Liu, C.-H., Liao, P.-Y., Lai, J.-C., Yang, J.-H. Tags: Research Articles Source Type: research
Quantitative assessment of the high-light tolerance in plants with an impaired photosystem II donor side
This study shows that through the use of PSII donor-side inhibitors, such as UV-B and Cd2+, there is a steeper gradient of photoinactivation in the systems with a weakened donor side, independent of the level of NPQ attained. This is coupled with a concomitant decline in the light tolerance of PSII. The native light tolerance is partially restored upon the use of 1,5-diphenylcarbazide (DPC), a PSII electron donor, allowing for the balance between the inhibitory pathways to be sensitively quantified. Thus, this study confirms that the impact of donor-side inhibition can be detected alongside acceptor-side photoinhibition us...
Source: Biochemical Journal - May 14, 2019 Category: Biochemistry Authors: Wilson, S., Ruban, A. V. Tags: Research Articles Source Type: research
Tubulin heterogeneity regulates functions and dynamics of microtubules and plays a role in the development of drug resistance in cancer
Microtubules, composed of αβ-tubulin heterodimers, exhibit diverse structural and functional properties in different cell types. The diversity in the microtubule structure originates from tubulin heterogeneities, namely tubulin isotypes and their post-translational modifications (PTMs). These heterogeneities confer differential stability to microtubules and provide spatial cues for the functioning of the cell. Furthermore, the altered expressions of tubulin isotypes and PTMs are prominent factors for the development of resistance against some cancer drugs. In this review, we summarize our current knowledge of th...
Source: Biochemical Journal - May 11, 2019 Category: Biochemistry Authors: Prassanawar, S. S., Panda, D. Tags: Review Articles Source Type: research
CrmA orthologs from diverse poxviruses potently inhibit caspases-1 and -8, yet cleavage site mutagenesis frequently produces caspase-1-specific variants
Poxviruses encode many proteins that enable them to evade host anti-viral defense mechanisms. Spi-2 proteins, including Cowpox virus CrmA, suppress anti-viral immune responses and contribute to poxviral pathogenesis and lethality. These proteins are ‘serpin’ protease inhibitors, which function via a pseudosubstrate mechanism involving initial interactions between the protease and a cleavage site within the serpin. A conformational change within the serpin interrupts the cleavage reaction, deforming the protease active site and preventing dissociation. Spi-2 proteins like CrmA potently inhibit caspases-1, -4 and...
Source: Biochemical Journal - May 6, 2019 Category: Biochemistry Authors: Bloomer, D. T., Kitevska-Ilioski, T., Pantaki-Eimany, D., Ji, Y., Miles, M. A., Heras, B., Hawkins, C. J. Tags: Research Articles Source Type: research
Starvation-induced autophagy is up-regulated via ROS-mediated ClC-3 chloride channel activation in the nasopharyngeal carcinoma cell line CNE-2Z
In this study, Earle's balanced salt solution (EBSS) was used to induce autophagy in CNE-2Z cells. We found that autophagy and the chloride current induced by EBSS were inhibited by chloride channel blockers. ClC-3 knockdown inhibited the degradation of LC3-II and P62. Furthermore, when reactive oxygen species (ROS) generation was suppressed by antioxidant N-acetyl-l-cysteine (L-NAC) pretreatment, EBSS-induced autophagy was inhibited, and the chloride current was unable to be activated. Nevertheless, ClC-3 knockdown had little effect on ROS levels, indicating that ROS acted upstream of ClC-3 and that both ROS and ClC-3 par...
Source: Biochemical Journal - May 6, 2019 Category: Biochemistry Authors: Zheng, Y., Chen, Z., Gu, Z., Yang, X., Yu, M., Zhao, C., Lin, J., Xu, P., Zhu, L., Jacob, T. J. C., Peng, S., Chen, L., Wang, L. Tags: Research Articles Source Type: research
PAS domain-containing phosphoglycerate kinase deficiency in Leishmania major results in increased autophagosome formation and cell death
Per-Arnt-Sim (PAS) domains are structurally conserved and present in numerous proteins throughout all branches of the phylogenetic tree. Although PAS domain-containing proteins are major players for the adaptation to environmental stimuli in both prokaryotic and eukaryotic organisms, these types of proteins are still uncharacterized in the trypanosomatid parasites, Trypanosome and Leishmania. In addition, PAS-containing phosphoglycerate kinase (PGK) protein is uncharacterized in the literature. Here, we report a PAS domain-containing PGK (LmPAS-PGK) in the unicellular pathogen Leishmania. The modeled structure of N-termina...
Source: Biochemical Journal - April 29, 2019 Category: Biochemistry Authors: Adhikari, A., Biswas, S., Mukherjee, A., Das, S., Adak, S. Tags: Research Articles Source Type: research
Novel long-chain neurotoxins from Bungarus candidus distinguish the two binding sites in muscle-type nicotinic acetylcholine receptors
α-Bungarotoxins, a novel group of long-chain α-neurotoxins, manifest different affinity to two agonist/competitive antagonist binding sites of muscle-type nicotinic acetylcholine receptors (nAChRs), being more active at the interface of α– subunits. Three isoforms (α-BgTx-1–3) were identified in Malayan Krait (Bungarus candidus) from Thailand by genomic DNA analysis; two of them (α-BgTx-1 and 2) were isolated from its venom. The toxins comprise 73 amino acid residues and 5 disulfide bridges, being homologous to α-bungarotoxin (α-BgTx), a classical blocker of muscle-type...
Source: Biochemical Journal - April 25, 2019 Category: Biochemistry Authors: Utkin, Y. N., Kuch, U., Kasheverov, I. E., Lebedev, D. S., Cederlund, E., Molles, B. E., Polyak, I., Ivanov, I. A., Prokopev, N. A., Ziganshin, R. H., Jornvall, H., Alvelius, G., Chanhome, L., Warrell, D. A., Mebs, D., Bergman, T., Tsetlin, V. I. Tags: Research Articles Source Type: research
