Water-mediated structural rearrangement establishes active conformation of caspases for apoptosis and inflammation.

Caspases are cysteine-dependent aspartate-specific proteases that play a crucial role in apoptosis (or programmed cell death) and inflammation. Based on their function, caspases are majorly categorized into apoptotic (initiator/apical and effector/executioner) and inflammatory caspases. Caspases undergo transition from an inactive zymogen to an active caspase to accomplish their function. This transition demands structural rearrangements which are most prominent at the active site loops and are imperative for the catalytic activity of caspases. In effector caspase-3, the structural rearrangement in the active site loop is shown to be facilitated by a set of invariant water (IW) molecules. However, the atomic details involving their role in stabilizing the active conformation have not been reported yet. Moreover, it is not known whether water molecules are essential for the active conformation in all caspases. Thus, in this study, we located IW molecules in initiator, effector, and inflammatory caspases to understand their precise role in rendering the structural arrangement of active caspases. Furthermore, IW molecules involved in anchoring the fragments of the protomer and rendering regulated flaccidity to caspases were identified. Location and identification of IW molecules interacting with amino acid residues involved in establishing the active conformation in the caspases might facilitate the design of potent inhibitors during up-regulated caspase activity in neurodegenerative and immune disorders. Communicated by Ramaswamy H. Sarma.

Identification and characterization of ABC transporters for carbohydrate uptake in Thermus thermophilus HB8.

Organisms use a variety of carbohydrates and metabolic pathways in order to capitalize in their specific environments. Depending upon their habitat, organism employs different types of transporters to maintain the cellular nutritional balance via central metabolism. A major contributor in this process in bacteria is a carbohydrate ABC transporter. The focus of this study is to get an insight into the carbohydrate transport and metabolism of a hot-spring-dwelling bacterium Thermus thermophilus HB8. We applied high-throughput data-mining approaches for identification and characterization of carbohydrate ABC transporters in T. thermophilus HB8. This enabled the identification of 11 putative carbohydrate ABC transport systems. To identify the cognate ligands for these transporters, functional annotation was performed. However, scarcity of homologous-protein's function hinders the process of functional annotation. Thus, to overcome this limitation, we integrated the functional annotation of carbohydrate ABC transporters with their metabolic analysis. Our results demonstrate that out of 11 putative carbohydrate ABC transporters, six are involved in the sugar (four for monosaccharides and polysaccharides-degraded products and two for osmotic regulation), four in phospholipid precursor (namely UgpABCE) and the remaining one in purine uptake. Further, analysis suggests the existence of sharing mechanism of transmembrane domains (TMDs) and/or nucleotide-binding domains (NBDs) among the 11 carbohydrate ABC transporters.

Designating ligand specificities to metal uptake ABC transporters in Thermus thermophilus HB8.

Micronutrients such as metal ions are indispensable for the growth and survival of microorganisms in assorted environmental niches. However, change in cellular concentration of metal ions is pernicious for an organism; thus metal ion homeostasis is crucial for their survival and growth. An eminent mechanism for maintaining metal ion homeostasis in microorganisms is ATP-binding cassette (ABC) transporters, which transport metal ions in their ionic/complex forms across the cell membrane. For the uptake, metals are sequestered by substrate-binding proteins (SBPs) and transferred to transmembrane domains (TMDs) for their transport. In this work, a high-throughput data mining analysis has been performed to identify open reading frames (ORFs) encoding metal-specific ABC transporters in a thermophilic bacterium Thermus thermophilus HB8. In total, 22 ORFs resulting in eight ABC transport systems were identified, which are potentially involved in the uptake of metal ions. This study suggests that three out of eight metal-specific ABC import systems are specific to iron ions. Among the remaining five, two are particular to divalent metal ions such as Mg2+ and Zn2+/Mn2+, another two are for tetrahedral oxyanions such as MoO42- and WO42- and the remaining one imports cyanocobalamin (vitamin B12). Besides these, the results of this study demonstrate the existence of a mechanism where TMD and NBD components are shared among different ABC transport systems hinting that multiple substrates can be imported via a single transporter. This study thus provides the first ever preliminary glimpse into the entire repertoire of metal uptake ABC transporters in a thermophilic organism.

Bioremediation of Congo red dye in immobilized batch and continuous packed bed bioreactor by Brevibacillus parabrevis using coconut shell bio-char.

In the present study, bacterial species capable of degrading colour waste were isolated from the water bodies located near the carpet cluster in the Bhadohi district of U.P., India. Among the isolated species best one was selected on the basis of its capability to degrade Congo red in batch experiments using NaCl-Yeast as the nutrient media and further it was identified as Brevibacillus parabrevis using 16S rDNA sequencing. The process parameters were optimized for maximum degradation in batch experiments and found out to be: Inoculum size: 3 ml, Temperature: 30 °C, Time: 6 days leading to a removal of 95.71% of dye sample. The experiment showed that bacteria immobilized with coconut shell biochar in continuous mode showed much better degradation than batch study without immobilization. The kinetics parameters µmax, Ks, and µmaxKs were found to be 0.461 per day, 39.44 mg/day, and 0.0117 L/mg/day using Monod model.