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Vikas Jain

Publications and source records attributed to Vikas Jain.

12 recordsLinked to original sources
PubMed2006

Synthesis and hydrolysis of pppGpp in mycobacteria: a ligand mediated conformational switch in Rel.

Bacteria respond to starvation by synthesizing a polyphosphate derivative of guanosine, (p)ppGpp, that helps the bacteria in surviving during stress. The protein in Gram-positive organisms required for (p)ppGpp synthesis is Rel, a bifunctional enzyme that carries out both synthesis and hydrolysis of this molecule. Rel shows increased pppGpp synthesis in the presence of uncharged tRNA, the effect of which is regulated by the C-terminal of Rel. We show by fluorescence resonance energy transfer that the distance between the N-terminus cysteine residue at the catalytic domain and C692 at the C-terminus increases upon the addition of uncharged tRNA. In apparent anomaly, the steady state anisotropy of the Rel protein decreases upon tRNA binding suggesting "compact conformation" vis-à-vis "open conformation" of the free Rel. We propose that the interaction between C692 and the residues present in the pppGpp synthesis site results in the regulated activity and this interaction is abrogated upon addition of uncharged tRNA. We also report here the binding of pppGpp to the C-terminal part of the protein that leads to more unfolding in this region.

Amino Acid Sequence↗
PubMed2006

Molecular dissection of the mycobacterial stringent response protein Rel.

Latency in Mycobacterium tuberculosis poses a barrier in its complete eradication. Overexpression of certain genes is one of the factors that help these bacilli survive inside the host during latency. Among these genes, rel, which leads to the expression of Rel protein, plays an important role by synthesizing the signaling molecule ppGpp using GDP and ATP as substrates, thereby changing bacterial physiology. In Gram-negative bacteria, the protein is thought to be activated in vivo in the presence of ribosome by sensing uncharged tRNA. In the present report, we show that Rel protein from Mycobacterium smegmatis, which is highly homologous to M. tuberculosis Rel, is functional even in the absence of ribosome and uncharged tRNA. From the experiments presented here, it appears that the activity of Rel(Msm) is regulated by the domains present at the C terminus, as the deletion of these domains results in higher synthesis activity, with little change in hydrolysis of ppGpp. However, in the presence of tRNA, though the synthesis activity of the full-length protein increases to a certain extent, the hydrolysis activity undergoes drastic reduction. Full-length Rel undergoes multimerization involving interchain disulfide bonds. The synthesis of pppGpp by the full-length protein is enhanced in the reduced environment in vitro, whereas the hydrolysis activity does not change significantly. Mutations of cysteines to serines result in monomerization with a simultaneous increase in the synthesis activity. Finally, it has been possible to identify the unique cysteine, of six present in Rel, required for tRNA-mediated synthesis of ppGpp.

Amino Acid Sequence↗
PubMed2006

ppGpp: stringent response and survival.

Adaptation to any undesirable change in the environment dictates the survivability of many microorganisms, with such changes generating a quick and suitable response, which guides the physiology of bacteria. During nutritional deprivation, bacteria show a stringent response, as characterized by the accumulation of (p)ppGpp, resulting in the repression of stable RNA species, such as rRNA and tRNA, with a concomitant change in colony morphology. However, genes involved in amino acid biosynthesis become over-expressed to help bacteria survive under such conditions. The survivability of pathogenic bacteria inside a host cell also depends upon the stringent response demonstrated. Therefore, an understanding of the physiology of stringent conditions becomes very interesting in regulation of the growth and persistence of such invading pathogens.

Amino Acid Sequence↗
PubMed2006

Piperacillin-tazobactam-induced drug hypersensitivity syndrome.

The drug hypersensitivity syndrome (DHS) is a rare but serious and potentially life-threatening reaction to common drugs in predisposed individuals. The syndrome is a triad of fever, skin eruption, and internal organ involvement. Prompt identification and discontinuation of the offending drug with symptomatic treatment of toxic effects is the mainstay of therapy for DHS.

Adult↗
PubMed2006

Neonatal priapism associated with spontaneous bilateral pyocavernositis.

INTRODUCTION: Neonatal priapism is known to be associated with a wide range of aetiologies, but an association with spontaneous purulent cavernositis has not been reported in the paediatric literature. We report the first of such case. CLINICAL PICTURE: A 24-day-old neonate was brought with the history of persistent erection of penis since day 4 of life and swollen penis of 4 days' duration, which revealed frank pus on cavernosal aspiration bilaterally. TREATMENT: The child was treated with closed aspiration drainage; cross-irrigation with antibiotic solution under systemic antibiotic cover helped in achieving complete detumescence. OUTCOME: On follow-up, child demonstrated normal full bladder tumescence and colour doppler revealed bilateral normal corporo-cavernosal appearance and blood flow, indicating good functional and anatomical recovery. CONCLUSION: This case report describes the presentation, successful management and excellent functional and anatomical outcome, on follow-up, of this rare association of neonatal priapism with spontaneous bilateral pyocavernositis. An attempt has been made to describe the underlying pathophysiology.

Algorithms↗
PubMed2005

Phase I clinical trial of BMS-247550, a derivative of epothilone B, using accelerated titration 2B design.

PURPOSE: BMS-247550 is a semisynthetic derivative of epothilone B with mechanism of action analogous to paclitaxel. It has shown impressive antitumor activity in preclinical studies including in taxane-resistant models. We conducted a phase I trial, based on accelerated titration "2B" design, of BMS-247550 given as a 1-hour infusion every 3 weeks. EXPERIMENTAL DESIGN: Seventeen patients (M:F, 10:7; median age, 54 years; performance status, 0-2) were treated on the trial. Forty-five cycles (1-9 cycles) of BMS-247550 were given at dosages ranging from 7.4 to 56 mg/m2. All patients received prophylaxis for hypersensitivity reactions, related to Cremophor-EL, with steroids and histamine antagonists. RESULTS: First-course dose-limiting toxicity (DLT) was observed in two of three patients at 56 mg/m2 (neutropenic sepsis, prolonged grade 4 neutropenia) and in one of six patients at 40 mg/m2. Nonhematologic grade 3 to 4 toxicities observed were emesis and fatigue and they occurred only at 56 mg/m2. Grade 1 to 2 peripheral neuropathy was also observed. Other grade 1 to 2 toxicities were myalgias, arthralgias, rash, hand/foot syndrome, and mucositis. AUC and C(max) seemed proportional to the dose and the DLT. Development of neutropenia with BMS-247550 is related to the duration of drug exposure above a threshold. CONCLUSIONS: The maximum tolerated dose (MTD) of BMS-247550 is 40 mg/m2 given every 3 weeks. Neutropenia is the DLT. The accelerated titration "2B" design may help in determining MTD with fewer patients enrolled and more being treated closer to the MTD. However, the accelerated titration design did not seem to shorten the study duration.

Adult↗
PubMed2005

Identification and characterization of rel promoter element of Mycobacterium tuberculosis.

The rel gene is responsible for the maintenance of the level of (p)ppGpp in bacteria under nutrient starvation. This phenomenon known as stringent response plays an important role during survival of the microorganisms in stationary phase. We have cloned 1.6 kb upstream sequence of rel gene of Mycobacterium tuberculosis in a shuttle vector pSD5B containing promoterless lacZ gene and promoter activity was observed in Mycobacterium smegmatis cells by blue/white selection and was measured by beta-galactosidase assay. In order to delineate the minimal promoter element of rel gene, a 200 bp fragment from this 1.6 kb upstream sequence was further cloned in promoterless lacZ shuttle vector pSD5B and promoter activity was observed in M. smegmatis cells in similar way. The 200 bp promoter fragment was found to be mycobacterium specific and did not respond when transformed in Escherichia coli. The +1 transcription start site was determined by primer extension method. The -10 promoter region was identified to be TATCCT. The three T bases when mutated, showed a remarkable decrease in the lacZ expression thus confirming the -10 region. The translation start site has also been identified by site directed frame shift mutagenesis. It appears that this rel promoter can be used for expression of proteins in mycobacteria.

5' Flanking Region↗
PubMed2003

Effect of abana (a herbal preparation) on the radiation-induced mortality in mice.

The effect of various doses (0, 5, 10, 20, 40 and 80 mg/kg body weight) of 50% ethanolic extract of abana, a traditional herbal preparation, widely used in India for the treatment of heart ailments, was studied on the radiation-induced mortality in mice exposed to 10 Gy of gamma-radiation. Treatment of mice with different doses of abana delayed the onset of mortality and reduced the symptoms of radiation sickness as compared to the irradiated controls. All doses of abana provided protection against the gastrointestinal (GI) death, however, the highest protection against GI death was observed for 20mg/kg abana. Pretreatment of mice with 20mg/kg abana provided the best protection as evidenced by the highest number of survivors after 30 days post-irradiation in this group when compared to the other doses of abana. Acute toxic studies revealed that the abana was non-toxic up to a dose of 1.6g/kg, where no drug-induced mortality was observed. The LD(50) dose of abana was found to be 1.8 g/kg body weight. Our study demonstrates the ability of abana as a good radioprotective agent and the optimum protective dose of abana was 1/90 of its LD(50) dose.

Animals↗
PubMed2002

Sugars have potential to curtail oxygenase activity of Rubisco.

Sugars play a critical role in regulating overall cellular metabolism and owing to their general compatibility with various cellular events plants invariably show enhanced levels of sugars for maintaining desired osmoticum under osmotic stress. Sugars (sucrose and trehalose) and sugar-alcohols (glycerol, mannitol, inositol, and sorbitol) with the exception of sorbitol lowered oxygenase activity of Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39) without altering carboxylase activity under unstressed conditions. Most interestingly, these solutes including sorbitol fully curtailed NaCl-induced enhancement in oxygenase activity, even at concentrations as low as 50mM. However, none of these solutes could alleviate NaCl-suppressed carboxylase activity. In summary, our findings demonstrate that one of the most important roles of sugars and sugar-alcohols in plants exposed to salt stress is to curtail oxygenase activity of Rubisco.

Carbohydrates↗