Ferric ion (hydr)oxo clusters in the “Venus flytrap” cleft of FbpA: M?ssbauer, calorimetric and mass spectrometric studies

Isothermal calorimetric studies of the binding of iron(III) citrate to ferric ion binding protein from Neisseria gonorrhoeae suggested the complexation of a tetranuclear iron(III) cluster as a single step binding event (apparent binding constant K(app) (ITC) = 6.0(5) × 10(5) M(-1)). High-resolution Fourier transform ion cyclotron resonance mass spectrometric data supported the binding of a tetranuclear oxo(hydroxo) iron(III) cluster of formula [Fe(4)O(2)(OH)(4)(H(2)O)(cit)](+) in the interdomain binding cleft of FbpA. The mutant H9Y-nFbpA showed a twofold increase in the apparent binding constant [K(app) (ITC) = 1.1(7) × 10(6) M(-1)] for the tetranuclear iron(III) cluster compared to the wild-type protein. M?ssbauer spectra of Escherichia coli cells overexpressing FbpA and cultured in the presence of added (57)Fe citrate were indicative of the presence of dinuclear and polynuclear clusters. FbpA therefore appears to have a strong affinity for iron clusters in iron-rich environments, a property which might endow the protein with new biological functions.     

Comparative genome analysis of the high pathogenicity Salmonella Typhimurium strain UK-1

Salmonella enterica serovar Typhimurium, a gram-negative facultative rod-shaped bacterium causing salmonellosis and foodborne disease, is one of the most common isolated Salmonella serovars in both developed and developing nations. Several S. Typhimurium genomes have been completed and many more genome-sequencing projects are underway. Comparative genome analysis of the multiple strains leads to a better understanding of the evolution of S. Typhimurium and its pathogenesis. S. Typhimurium strain UK-1 (belongs to phage type 1) is highly virulent when orally administered to mice and chickens and efficiently colonizes lymphoid tissues of these species. These characteristics make this strain a good choice for use in vaccine development. In fact, UK-1 has been used as the parent strain for a number of nonrecombinant and recombinant vaccine strains, including several commercial vaccines for poultry. In this study, we conducted a thorough comparative genome analysis of the UK-1 strain with other S. Typhimurium strains and examined the phenotypic impact of several genomic differences. Whole genomic comparison highlights an extremely close relationship between the UK-1 strain and other S. Typhimurium strains; however, many interesting genetic and genomic variations specific to UK-1 were explored. In particular, the deletion of a UK-1-specific gene that is highly similar to the gene encoding the T3SS effector protein NleC exhibited a significant decrease in oral virulence in BALB/c mice. The complete genetic complements in UK-1, especially those elements that contribute to virulence or aid in determining the diversity within bacterial species, provide key information in evaluating the functional characterization of important genetic determinants and for development of vaccines.     

Novel and potent oxazolidinone antibacterials featuring 3-indolylglyoxamide substituents

Novel oxazolidinone antibacterials bearing a variety of 3-indolylglyoxamide substituents have been explored in an effort to improve the spectrum and potency of this class of agents. A subclass of this series was also made with the diversity at C-5 terminus. These derivatives have been screened against a panel of clinically relevant Gram-positive pathogens and fastidious Gram-negative organisms. Several analogs in this series were identified with in vitro activity superior to linezolid (MIC=0.25-2 microg/mL). Compounds 10a, 10c, 10e and 10f displayed activity against linezolid resistant Gram-positive organisms (MIC=2-4 microg/mL). Selected oxazolidinones were evaluated for in vivo efficacy against a mouse systemic infection model.     

An insight into the active site of a type I DNA topoisomerase from the kinetoplastid protozoan Leishmania donovani

DNA topoisomerases are ubiquitous enzymes that govern the topological interconversions of DNA thereby playing a key role in many aspects of nucleic acid metabolism. Recently determined crystal structures of topoisomerase fragments, representing nearly all the known subclasses, have been solved. The type IB enzymes are structurally distinct from other known topoisomerases but are similar to a class of enzymes referred to as tyrosine recombinases. A putative topoisomerase I open reading frame from the kinetoplastid Leishmania donovani was reported which shared a substantial degree of homology with type IB topoisomerases but having a variable C-terminus. Here we present a molecular model of the above parasite gene product, using the human topoisomerase I crystal structure in complex with a 22 bp oligonucleotide as a template. Our studies indicate that the overall structure of the parasite protein is similar to the human enzyme; however, major differences occur in the C-terminal loop, which harbors a serine in place of the usual catalytic tyrosine. Most other structural themes common to type IB topoisomerases, including secondary structural folds, hinged clamps that open and close to bind DNA, nucleophilic attack on the scissile DNA strand and formation of a ternary complex with the topoisomerase I inhibitor camptothecin could be visualized in our homology model. The validity of serine acting as the nucleophile in the case of the parasite protein model was corroborated with our biochemical mapping of the active site with topoisomerase I enzyme purified from L.donovani promastigotes.     

The Socioeconomic and Institutional Determinants of Participation in India’s Health Insurance Scheme for the Poor

The Rashtriya Swasthya Bima Yojana (RSBY), which was introduced in 2008 in India, is a social health insurance scheme that aims to improve healthcare access and provide financial risk protection to the poor. In this study, we analyse the determinants of participation and enrolment in the scheme at the level of districts. We used official data on RSBY enrolment, socioeconomic data from the District Level Household Survey 2007–2008, and additional state-level information on fiscal health, political affiliation, and quality of governance. Results from multivariate probit and OLS analyses suggest that political and institutional factors are among the strongest determinants explaining the variation in participation and enrolment in RSBY. In particular, districts in state governments that are politically affiliated with the opposition or neutral parties at the centre are more likely to participate in RSBY, and have higher levels of enrolment. Districts in states with a lower quality of governance, a pre-existing state-level health insurance scheme, or with a lower level of fiscal deficit as compared to GDP, are significantly less likely to participate, or have lower enrolment rates. Among socioeconomic factors, we find some evidence of weak or imprecise targeting. Districts with a higher share of socioeconomically backward castes are less likely to participate, and their enrolment rates are also lower. Finally, districts with more non-poor households may be more likely to participate, although with lower enrolment rates.     

Association of Endogenous Testosterone with Lipid and Blood Glucose Profiles in Elderly Men with Angiographically Proven Cardiovascular Disease of Nadia and Murshidabad District,West Bengal

Testosterone is commonly known for its role in the regulation of reproductive physiology in men. Epidemiologic studies suggest that endogenous testosterone levels may be implicated in cardiovascular diseases (CVDs). Our study aimed to investigate the relationship between serum total testosterone (TT) levels and lipid profile as well as fasting blood glucose (FBG) levels in male patients ranging from 40 to 70 years old with angiographically proven CVDs from Nadia and Murshidabad district of West Bengal, India. These data were compared with the normal men with no CVD history. We observed a significantly low serum TT levels in CVD patient group compared to the normal group. Among CVD patients, a significant (p < 0.05) negative association was found between serum TT and total cholesterol, triglyceride, low density lipoprotein and very low density lipoprotein, whereas a significant positive correlation (p < 0.05) was found between serum TT and high density lipoprotein. We also observed a highly significant negative correlation between TT and FBG levels in CVD patient group. Thus, in these two densely populated district of West Bengal with poor socio-economic condition, low levels of serum TT in elderly men is associated with CVD that appear together with an atherogenic lipid milieu that may be involved in the pathogenesis of CVD. Results further indicate that low serum TT might have a role in the development of hyperglycemia as evidenced from high FBG level in elderly men.