Magnetic resonance studies on the interaction of metal-ion and nucleotide ligands with brain hexokinase

Our previous studies have shown that one manganous ion binds tightly to bovine brain hexokinase, with a Kd =25 ± 4 μM. The characteristic proton relaxation rate (PRR) enhancement of this binary complex (εb) 3 .5 at 9 MHz and 23 °C [ Jarori, G. K. Kasturi, S. R., and Kenkare, U. W. (1981) Arch. Biochem. Biophys. 211,258 - 2681. On the basis of PRR enhancement patterns, observed on the addition of nucleotides ATP and ADP to this E . Mn binary complex, we now show the formation of a nucleotide-bridge ternary complex, enzyme . nucleotide . Mn. Addition of glucose 6-phosphate to enzyme . ATP . Mn, results in a competitive displacement of ATP Mn from the enzyme. However, a quaternary complex E · ADP· Mn· Glc-6-P appears to be formed when both the products are present. β, γ-Bidentate Cr(II1)ATP has been used to elucidate the role of direct binding of Mn(I1) in catalysis, and the stoichiometry of metal-ion interaction with the enzyme in the presence of nucleotide. Bidentate Cr(II1)ATP serves as a substrate for brain hexokinase without any additional requirement for a divalent cation. However, electron-spin resonance studies on the binding of Mn(I1) to the enzyme in the presence of Cr(I1I)ATP suggest that, in the presence of nucleotide, two metal ions interact with hexokinase, one binding directly to the enzyme and the second interacting via the nucleotide bridge. It is this latter one which participates in catalysis. Experiments carried out with hexokinase spin-labeled with 3-(2-iodo-acetamido)-2,2,5,5-tetramethyl-lpyrrolidinyloxyl clearly showed that the direct-binding Mn site on the enzyme is distinctly located from its ATP Mn binding site

Integrated Physiological, Biochemical, and Molecular Analysis Identifies Important Traits and Mechanisms Associated with Differential Response of Rice Genotypes to Elevated Temperature

In changing climate, heat stress caused by high temperature poses a serious threat to rice cultivation. A multiple organizational analysis at physiological, biochemical and molecular level is required to fully understand the impact of elevated temperature in rice. This study was aimed at deciphering the elevated temperature response in eleven popular and mega rice cultivars widely grown in India. Physiological and biochemical traits specifically membrane thermostability (MTS), antioxidants, and photosynthesis were studied at vegetative and reproductive phases which were used to establish a correlation with grain yield under stress. Several useful traits in different genotypes were identified which will be important resource to develop high temperature tolerant rice cultivars. Interestingly, Nagina22 emerged as best performer in terms of yield as well as expression of physiological and biochemical traits at elevated temperature. It showed lesser relative injury, lesser reduction in chlorophyll content, increased super oxide dismutase, catalase and peroxidase activity, lesser reduction in net photosynthetic rate (PN), high transpiration rate (E) and other photosynthetic/ fluorescence parameters contributing to least reduction in spikelet fertility and grain yield at elevated temperature. Further, expression of 14 genes including heat shock transcription factors and heat shock proteins was analyzed in Nagina22 (tolerant) and Vandana (susceptible) at flowering phase, strengthening the fact that N22 performs better at molecular level also during elevated temperature. This study shows that elevated temperature response is complex and involves multiple biological processes which are needed to be characterized to address the challenges of future climate extreme conditions

Not Available

Not AvailableHigh-temperature stress is a major abiotic stress that affects various biological processes Of plants Such as biochemical and physiological response, growth, development, and yield. High-temperature Stress has critical effects at cellular and molecular levels also. The increased concentration of regulatory proteins such as heat shock transcription factors (Hsfs) is a major molecular response that occurs during heat stress. These regulatory proteins in turn regulate the expression of heat shock protein (HSP) genes that act as critical players during stress to maintain cell homeostasis. Besides HSPs, the other metabolic and regulatory genes, signalling compounds, compatible osmolytes, and antioxidants too play an important role during Heat stress in plants. Apart From the protein-coding genes, recent studies have shown that noncoding microns (miRNAs) Also play a key role during heat stress by modulating the gene expression at the transcription and post-transcriptional evel. The transcriptome approaches are important to understand the molecular and cellular changes occurring in response to heat stress. The approaches rely mostly by adopting the traditional methods like Northern blot/RNA blot and reverse transcription PCR (RT-PCR), Where the expression of the genes can be studied in different tissues and cells, whereas the extent of their expression can be achieved by quantitative PCR Or real time PCR. Further, The genome-wide expression profiling tools such as microarray analysis, next-generation sequencing, and RNA Sequencing offer a great potential in this direction. This chapter primarily provides the current understanding on the role of regulatory genes (transcription factors), HSP genes, metabolic genes, signaling compounds, osmolytes, reactive oxygen species, and miRNAs as well as other small RNAs of plants under high temperature. In addition, it gives a brief account of various transcriptome approaches to study the expression profiling of genes during heat stress.Not Availabl

Binding mechanism of methyl-α-N-acetyl-D-galactopyranosyl amine to <i>Artocarpus lakoocha </i>lectin, artocarpin: A proton nuclear magnetic resonance study

299-306The dynamics of the binding mechanism between Artocarpus lakoocha lectin and Me-α-D-GalNAc has been studied using 1H NMR spectroscopy. Various thermodynamic parameters have been calculated with the help of temperature dependence of line broadening of the methoxy group resonance of Me-α-D-GalNAc. No change in the chemical shift has been observed while full line width at half height of the sugar protons was found to increase with increasing temperature indicating that the binding ligand is in fast exchange. No chemical shift between bound and free ligands has been observed.The activation parameters obtained from the association and dissociation rate constants suggest that the association process is controlled by high activation entropy which is due to the specific orientation of both lectin and sugar whereas the contribution of activation enthalpy is small. On the other hand, the dissociation reaction is controlled by high activation enthalpy due to the break in the interaction between the sugar and the lectin. From NMR data a two-step binding mechanism has been proposed. The associated complex is stabilized mainly by hydrogen bonding and vander Waals attractions while hydrophobic interaction is not significant as indicated by the negative entropy and enthalpy values

International encyclopaedia of Indian literature /

2. Tamil3. Assamese4. Kannada5. Telugu6. Malayalam7. Urdu8. Sindh