Biology subjects

Jena, A. K.

Publications and source records attributed to Jena, A. K..

5 recordsLinked to original sources

bioRxiv2026

Unravelling the plausible metal-dependent catalytic mechanism of Inositol monophosphatase ortholog from Pseudomonas aeruginosa through the lenses of macromolecular crystallography and enzyme kinetics

The inositol monophosphatase (IMPase) orthologue is pivotal for virulence, pathogenesis, and biofilm regulation, and is therefore considered a potential drug target in Pseudomonas aeruginosa and other bacterial pathogens. The mammalian IMPase orthologue is an established drug target for bipolar disorder. The precise catalytic mechanism in this class of enzymes remains obscure despite five to six decades of extensive efforts and detailed studies of substrate, transition-state analogue, and product-bound structures. Here, we have solved the crystal structures of the IMPase orthologue from Pseudomonas aeruginosa (PaIMPase), capturing pre- and post-catalytic snapshots of metal-substrate- and metal-product-mimic-bound states. Moreover, we solved the metal-substrate transition-state-analogue-bound crystal structure of the enzyme. Critical evaluation of these high-resolution crystal structures of PaIMPase complexed with substrate, transition-state analogue, and product mimic (myo-inositol and phosphate) supports three Mg2+-dependent catalytic mechanisms of PaIMPase. The structural snapshots indicate that, at the enzyme active site, a metal (Mg2+)-coordinating water molecule, activated by two bound Mg2+ ions and the active-site-proximal Threonine/Aspartate dyad, attacks the central phosphorus atom of the bound substrate, leading to formation of a trigonal bipyramidal transition state. Following that, the immediate breakdown of the P-O bond results in the formation of inositolate and phosphate ions. The second water molecule, activated by another Mg2+ dyad, facilitates the departure of myo-inositol and phosphate from the active site. The detailed mechanistic insights gained from this work may offer a foundation for the rational design of precise inhibitors against PaIMPase.

biophysics↗

bioRxiv2025

Suppressing the suppressor: Gallic acid induced asymmetric tetramerization of the pleotropic virulence factor SuhB from Pseudomonas aeruginosa abolishes its extragenic suppressor activities. A structure-based functional study

Pseudomonas aeruginosa SuhB (PaSuhB) is a member of the bacterial Inositol monophosphatase family proteins. Numerous scientific evidences suggest PaSuhB is the pleotropic regulator of different metabolic pathways involved in bacterial biofilm formation and virulence determination. In this study, we have solved the high-resolution crystal structures of PaSuhB in its apo and substrate (Inositol monophosphatase) bound forms. Moreover, we carried out 3D pharmacophore modelling of the bound substrate to identify gallic acid, a phyto-phenol, abundant in medicinal plants, as a novel PaSuhB inhibitor. The high-resolution crystal structure of gallic acid/PaSuhB binary complex leads to the identification of a novel allosteric ligand binding site of the protein. In vitro, gallic acid induces the cold-sensitive growth of P. aeruginosa and E. coli, the previously reported phenomenon observed in suhB deletion mutants and also inhibits the swimming motility of P. aeruginosa. The plausible anti-bacterial molecular mechanism of action of gallic acid is presented herein.

biophysics↗

bioRxiv2025

Tsc1 Deletion in Purkinje Neurons Disrupts the Axon Initial Segment, Impairing Excitability and Cerebellar Function

Loss-of-function mutations in tuberous sclerosis 1 (TSC1) are prevalent monogenic causes of autism spectrum disorder (ASD). Selective deletion of Tsc1 from mouse cerebellar Purkinje neurons has been shown to cause several ASD-linked behavioral impairments, which are linked to reduced Purkinje neuron repetitive firing rates. We used electrophysiology methods to investigate why Purkinje neuron-specific Tsc1 deletion (Tsc1mut/mut) impairs Purkinje neuron firing. These studies revealed a depolarized shift in action potential threshold voltage, an effect that we link to reduced expression of the fast-transient voltage-gated sodium (Nav) current in Tsc1mut/mut Purkinje neurons. The reduced Nav currents in these cells was associated with diminished secondary immunofluorescence from anti-pan Nav channel labeling at Purkinje neuron axon initial segments (AIS). Interestingly, anti-ankyrinG immunofluorescence was also found to be significantly reduced at the AIS of Tsc1mut/mut Purkinje neurons, suggesting Tsc1 is necessary for the organization and functioning of the Purkinje neuron AIS. An analysis of the 1st and 2nd derivative of the action potential voltage-waveform supported this hypothesis, revealing spike initiation and propagation from the AIS of Tsc1mut/mut Purkinje neurons is impaired compared to age-matched control Purkinje neurons. Heterozygous Tsc1 deletion resulted in no significant changes in the firing properties of adult Purkinje neurons, and slight reductions in anti-pan Nav and anti-ankyrinG labeling at the Purkinje neuron AIS, revealing deficits in Purkinje neuron firing due to Tsc1 haploinsufficiency are delayed compared to age-matched Tsc1mut/mut Purkinje neurons. Together, these data reveal the loss of Tsc1 impairs Purkinje neuron firing and membrane excitability through the dysregulation of proteins necessary for AIS organization and function.

neuroscience↗

bioRxiv2024

Selective deletion of Tsc1 from mouse cerebellar Purkinje neurons drives sex-specific behavioral impairments linked to autism

There is a striking sex bias in the prevalence and severity of autism spectrum disorder (ASD) with 80% of diagnoses occurring in males. Because the molecular etiology of ASD is likely combinatorial, including interactions across multiple genetic and environmental factors, it is difficult to investigate the physiological mechanisms driving sex-specific differences. Loss of function mutations in TSC1 result in dysregulated mTORC1 signaling and underlie a multi-system disorder known as tuberous sclerosis (TSC). Interestingly, more than 50% of individuals diagnosed with TSC are also diagnosed with ASD, making TSC mutations one of the most prevalent monogenic causes of ASD. Mice harboring targeted deletion of Tsc1 selectively in cerebellar Purkinje neurons, referred to here as Tsc1mut/mut, have multiple ASD-linked behavioral impairments, including deficits in social interactions, motor coordination, and vocalizations. However, these ASD-linked behavioral deficits have only been investigated using male Tsc1mut/mut animals. Here, we used cohorts of male and female Tsc1mut/mut animals to determine if behavioral impairments, previously identified in this model, are similar across sex. Specifically, we measured balance and motor coordination and social interaction behaviors in two age groups across sex. We determined balance and motor coordination deficits are similar in male and female Tsc1mut/mut mice, and that deficits in the firing of Tsc1mut/mut Purkinje neurons located in the cerebellar vermis are also similar across sex. However, impairments in social approach behavior were found to be significantly more severe in Tsc1mut/mut males compared to females. These results indicate the selective deletion of Tsc1 in Purkinje neurons differentially impairs cerebellar circuits based on sex.

neuroscience↗

bioRxiv2019

Larval growth and survival in Indian Butter Catfish, Ompok bimaculatus (Bloch): effect of light intensity and photoperiod

Two sequential indoor rearing trials each of 21 days duration were conducted to investigate the effect of light intensity and photoperiod respectively on the growth and survival of Ompok bimaculatus larvae. In first trial, five different light intensities viz. 0, 300, 500, 900, 1200 lx were applied randomly to 800 larvae (0.003 g; 0.51 cm) stocked in triplicate following a completely randomized design into aquarium (30.0 x 15.0 x 15.0 cm) tanks. Sequentially, in second trial, five photoperiod cycles (light: dark, L: D) namely, 24L: 0D, 16L: 8D, 12L: 12D, 8L: 16D and 0L: 24D in combination with the best performing light intensity (300 lx) as observed from the first trial were employed in triplicates in similar set up. From the first trial, significantly higher survival was observed in 0 and 300 lx, whereas growth was highest in 900 lx (P < 0.05). In the second trial, survival was higher in continuous darkness (0L: 24D), whereas, maximum growth was recorded in 24L: 0D and 16L: 8D groups (P < 0.05). Performance index (PI) showed no significant difference (P > 0.05) among 0 and 300 lx light intensities, but were reduced at higher light intensities. The lowest PI was found in 12L: 12D and 8L: 16D condition but did not have any effect in other photoperiod cycles. Overall, from the present study it can be concluded that growth of the larvae is found to be higher in higher light intensity (900lx) and longer photoperiodic cycles (24L: 0D and 16L: 8D), however, better survival was recorded in total dark conditions suggesting that continuous dark condition is recommended for better hatchery performance of the larvae.

animal behavior and cognition↗