Conformational selection underpins recognition of multiple DNA sequences by proteins and consequent functional actions.

Recognition of multiple functional DNA sequences by a DNA-binding protein occurs widely in nature. The physico-chemical basis of this phenomenon is not well-understood. The E. coli gal repressor, a gene regulatory protein, binds two homologous but non-identical sixteen basepair sequences in the gal operon and interacts by protein-protein interaction to regulate gene expression. The two sites have nearly equal affinities for the Gal repressor. Spectroscopic studies of the Gal repressor bound to these two different DNA sequences detected significant conformational differences between them. Comprehensive single base-substitution and binding measurements were carried out on the two sequences to understand the nature of the two protein-DNA interfaces. Magnitudes of basepair-protein interaction energy show significant variation between homologous positions of the two DNA sequences. Magnitudes of variation are such that when summed over the whole sequence they largely cancel each other out, thus producing nearly equal net affinity. Modeling suggests significant alterations in the protein-DNA interface in the two complexes, which are consistent with conformational adaptation of the protein to different DNA sequences. The functional role of the two sequences was studied by substitution of one site by the other and vice versa. In both cases, substitution reduces repression in vivo. This suggests that naturally occurring DNA sequence variations play functional roles beyond merely acting as high-affinity anchoring points. We propose that two different pre-existing conformations in the conformational ensemble of the free protein are selected by two different DNA sequences for efficient sequence read-out and the conformational difference of the bound proteins leads to different functional roles.

Enhancing aromatic rice production through agronomic and nutritional management for improved yield and quality.

To meet the growing international demand for aromatic rice, this study, conducted at Uttar Banga Krishi Viswavidyalaya in Cooch Behar, West Bengal, aimed to enhance the yield and quality of the 'Tulaipanji' rice cultivar through advanced establishment methods and the use of organic nutrients over two years. The research tested three planting techniques: mechanical transplanting, wet direct seeding (using a drum seeder), and traditional methods, alongside four nutrient management strategies: vermicompost, farmyard manure, a mix of both, and conventional fertilizers. Findings revealed that mechanical transplanting significantly increased yield by over 31.98% and 71.05% compared to traditional methods and wet direct seeding, respectively. Using vermicompost alone as a nutrient source not only boosted yields by 21.31% over conventional fertilizers but also enhanced the rice's nutritional value and cooking quality. Moreover, soils treated with vermicompost showed higher dehydrogenase activity, indicating better soil health. Economically, mechanical transplanting with vermicompost was the most beneficial, yielding the highest net returns and benefit-cost ratios in both years studied. This approach presents a viable model for improving the sustainability of aromatic rice production globally, emphasizing the economic and environmental advantages of adopting mechanical planting techniques and organic fertilization methods.

A functional loop spanning distant domains of glutaminyl-tRNA synthetase also stabilizes a molten globule state.

Molten globule and other disordered states of proteins are now known to play important roles in many cellular processes. From equilibrium unfolding studies of two paralogous proteins and their variants, glutaminyl-tRNA synthetase (GlnRS) and two of its variants [glutamyl-tRNA synthetase (GluRS) and its isolated domains, and a GluRS-GlnRS chimera], we demonstrate that only GlnRS forms a molten globule-like intermediate at low urea concentrations. We demonstrated that a loop in the GlnRS C-terminal anticodon binding domain that promotes communication with the N-terminal domain and indirectly modulates amino acid binding is also responsible for stabilization of the molten globule state. This loop was inserted into GluRS in the eukaryotic branch after the archaea-eukarya split, right around the time when GlnRS evolved. Because of the structural and functional importance of the loop, it is proposed that the insertion of the loop into a putative ancestral GluRS in eukaryotes produced a catalytically active molten globule state. Because of their enhanced dynamic nature, catalytically active molten globules are likely to possess broad substrate specificity. It is further proposed that the putative broader substrate specificity allowed the catalytically active molten globule to accept glutamine in addition to glutamic acid, leading to the evolution of GlnRS.

A chimaeric glutamyl:glutaminyl-tRNA synthetase: implications for evolution.

aaRSs (aminoacyl-tRNA synthetases) are multi-domain proteins that have evolved by domain acquisition. The anti-codon binding domain was added to the more ancient catalytic domain during aaRS evolution. Unlike in eukaryotes, the anti-codon binding domains of GluRS (glutamyl-tRNA synthetase) and GlnRS (glutaminyl-tRNA synthetase) in bacteria are structurally distinct. This originates from the unique evolutionary history of GlnRSs. Starting from the catalytic domain, eukaryotic GluRS evolved by acquiring the archaea/eukaryote-specific anti-codon binding domain after branching away from the eubacteria family. Subsequently, eukaryotic GlnRS evolved from GluRS by gene duplication and horizontally transferred to bacteria. In order to study the properties of the putative ancestral GluRS in eukaryotes, formed immediately after acquiring the anti-codon binding domain, we have designed and constructed a chimaeric protein, cGluGlnRS, consisting of the catalytic domain, Ec GluRS (Escherichia coli GluRS), and the anti-codon binding domain of EcGlnRS (E. coli GlnRS). In contrast to the isolated EcN-GluRS, cGluGlnRS showed detectable activity of glutamylation of E. coli tRNA(glu) and was capable of complementing an E. coli ts (temperature-sensitive)-GluRS strain at non-permissive temperatures. Both cGluGlnRS and EcN-GluRS were found to bind E. coli tRNA(glu) with native EcGluRS-like affinity, suggesting that the anticodon-binding domain in cGluGlnRS enhances k(cat) for glutamylation. This was further confirmed from similar experiments with a chimaera between EcN-GluRS and the substrate-binding domain of EcDnaK (E. coli DnaK). We also show that an extended loop, present in the anticodon-binding domains of GlnRSs, is absent in archaeal GluRS, suggesting that the loop was a later addition, generating additional anti-codon discrimination capability in GlnRS as it evolved from GluRS in eukaryotes.

Dependence of RF/Analog and Linearity Figure of Merits on Temperature in Ferroelectric FinFET: A Simulation Study.

This article presents a simulation study of the impact of variation in temperature on the transfer characteristics and the RF/analog performance like transconductance ( gm ), gate capacitance ( Cgg ), cutoff frequency ( ft ), and transconductance frequency product (TFP) of the ferroelectric FinFET (Fe-FinFET). In addition, the impact of temperature on the linearity parameters such as higher order harmonics ( gm2 and gm3 ), second- and third-order voltage intercept points (VIP2 and VIP3), third-order power-intercept point (IIP3), third-order intermodulation distortion (IMD3), and 1-dB compression point is estimated for wide variation of temperature in the Fe-FinFET. It is seen that temperature has a significant impact on the RF/analog and linearity parameters, and these figure of merits (FoMs) are the functions of temperature. Analysis reports that RF/analog parameters are suppressed, whereas the linearity FoMs are improved as temperature changed from 250 to 350 K.

Solvation change and ion release during aminoacylation by aminoacyl-tRNA synthetases.

Discrimination between cognate and non-cognate tRNAs by aminoacyl-tRNA synthetases occurs at several steps of the aminoacylation pathway. We have measured changes of solvation and counter-ion distribution at various steps of the aminoacylation pathway of glutamyl- and glutaminyl-tRNA synthetases. The decrease in the association constant with increasing KCl concentration is relatively small for cognate tRNA binding when compared to known DNA-protein interactions. The electro-neutral nature of the tRNA binding domain may be largely responsible for this low ion release stoichiometry, suggesting that a relatively large electrostatic component of the DNA-protein interaction free energy may have evolved for other purposes, such as, target search. Little change in solvation upon tRNA binding is seen. Non-cognate tRNA binding actually increases with increasing KCl concentration indicating that charge repulsion may be a significant component of binding free energy. Thus, electrostatic interactions may have been used to discriminate between cognate and non-cognate tRNAs in the binding step. The catalytic constant of glutaminyl-tRNA synthetase increases with increasing osmotic pressure indicating a water release of 8.4 +/- 1.4 mol/mol in the transition state, whereas little change is seen in the case of glutamyl-tRNA synthetase. We propose that the significant amount of water release in the transition state, in the case of glutaminyl-tRNA synthetase, is due to additional contact of the protein with the tRNA in the transition state.

The role of the catalytic domain of E. coli GluRS in tRNAGln discrimination.

Discrimination of tRNA(Gln) is an integral function of several bacterial glutamyl-tRNA synthetases (GluRS). The origin of the discrimination is thought to arise from unfavorable interactions between tRNA(Gln) and the anticodon-binding domain of GluRS. From experiments on an anticodon-binding domain truncated Escherichia coli (E. coli) GluRS (catalytic domain) and a chimeric protein, constructed from the catalytic domain of E. coli GluRS and the anticodon-binding domain of E. coli glutaminyl-tRNA synthetase (GlnRS), we show that both proteins discriminate against E. coli tRNA(Gln). Our results demonstrate that in addition to the anticodon-binding domain, tRNA(Gln) discriminatory elements may be present in the catalytic domain in E. coli GluRS as well.