An ecological study of the macrophytic vegetation of Doodhadhari Lake,Raipur, M. P. 3 chemical factors

Summary The paper is based on the monthly fluctuations of various chemical constituents studied at three stations established at different depths. It includes a discussion on the horizontal and vertical distribution of different chemical factors and their relationship with the distribution of plants in the lake. The factors studied are dissolved oxygen, free carbon dioxide, pH, alkalinity, specific conductivity, sodium, potassium, total hardness, calcium and magnesium.Part of the thesis submitted for the degree of doctor of philosophy     

Progesterone and prolactin are both required for suppression of the induction of rat alpha-lactalbumin activity

Progesterone prevents lactation during pregnancy. This anti-lactogenic effect includes suppression of the advent of alpha-lactalbumin activity, an effect which prevents the formation of lactose. Alpha lactalbumin activity can be induced to some extent in pregnant rat mammary explants by insulin and hydrocortisone alone, and to a greater extent with prolactin in addition, or with EGF in addition. Physiological levels of progesterone markedly inhibit the induction in the presence of prolactin plus insulin and hydrocortisone, only weakly inhibit in the presence of insulin and hydrocortisone alone, and have no inhibitory effect in the presence of EGF plus insulin and hydrocortisone. Prolactin permits some inhibition in the presence of EGF. The results suggest that progesterone does not subvert the essential insulin or glucocorticoid signals. It also appears that transduction of the prolactin signal is required in order that progesterone effectively block induction of alpha-lactalbumin activity.     

Insights into Mycoplasma genitalium metabolism revealed by the structure of MG289, an extracytoplasmic thiamine binding lipoprotein

Mycoplasma genitalium is one of the smallest organisms capable of self‐replication and its sequence is considered a starting point for understanding the minimal genome required for life. MG289, a putative phosphonate substrate binding protein, is considered to be one of these essential genes. The crystal structure of MG289 has been solved at 1.95 Å resolution. The structurally identified thiamine binding region reveals possible mechanisms for ligand promiscuity. MG289 was determined to be an extracytoplasmic thiamine binding lipoprotein. Computational analysis, size exclusion chromatography, and small angle X‐ray scattering indicates that MG289 homodimerizes in a concentration‐dependant manner. Comparisons to the thiamine pyrophosphate binding homolog Cypl reveal insights into the metabolic differences between mycoplasmal species including identifying possible kinases for cofactor phosphorylation and describing the mechanism of thiamine transport into the cell. These results provide a baseline to build our understanding of the minimal metabolic requirements of a living organism. Proteins 2011. © 2010 Wiley‐Liss, Inc.     

X-ray crystal structure of the UCS domain-containing UNC-45 myosin chaperone from Drosophila melanogaster

UCS proteins, such as UNC-45, influence muscle contraction and other myosin-dependent motile processes. We report the first X-ray crystal structure of a UCS domain-containing protein, the UNC-45 myosin chaperone from Drosophila melanogaster (DmUNC-45). The structure reveals that the central and UCS domains form a contiguous arrangement of 17 consecutive helical layers that arrange themselves into five discrete armadillo repeat subdomains. Small-angle X-ray scattering data suggest that free DmUNC-45 adopts an elongated conformation and exhibits flexibility in solution. Protease sensitivity maps to a conserved loop that contacts the most carboxy-terminal UNC-45 armadillo repeat subdomain. Amino acid conservation across diverse UCS proteins maps to one face of this carboxy-terminal subdomain, and the majority of mutations that affect myosin-dependent cellular activities lie within or around this region. Our crystallographic, biophysical, and biochemical analyses suggest that DmUNC-45 function is afforded by its flexibility and by structural integrity of its UCS domain.     

Molecular modelling of urease accessory interaction proteins of Helicobacter Pylori J 99 and predicting an interruption in interaction by Vigna radiata Defensins

Helicobacter pylori is the major causative agent of Gastric carcinoma. Significance of the urease accessory interaction proteins are emphasized in colonization of human gastric mucosa and efficient infection of H. pylori. Here an attempt is made to explore the structure and properties of urease accessory interaction proteins from Helicobacter pylori J 99. The proteins chosen for the study are ureH, ureI, nikR, groL and flgS based on the interaction map available from STRING database. The above mentioned proteins do not have a comprehensive three dimensional structure. Hence the models were generated using PSI-BLAST (Position Specific Iterative-Blast) and MODELLER 9V8. Physicochemical characterization encompasses pI, EC, AI, II and GRAVY. Secondary structure was predicted using PSI-PRED. Functional characterization was done by SOSUI and DISULFIND Servers and refinement of structure was done using Ramachandran plot analysis. RMS-Z values were calculated using Q-MEAN Server and CHIMERA was used for molecular simulation studies. Plant defensins from Vigna radiata are successfully docked to the modeled structures and thus interaction could be possibly prevented. These results will pave way for further selective inhibition of H. pylori colonization and in vivo survival by employing plant defensins from Vigna radiata (VrD1 & VrD2). The work will prove that plant defensins provides anticancer relief too.     

A Triple Mutant in the Ω-loop of TEM-1 β-Lactamase Changes the Substrate Profile via a Large Conformational Change and an Altered General Base for Catalysis

β-Lactamases are bacterial enzymes that hydrolyze β-lactam antibiotics. TEM-1 is a prevalent plasmid-encoded β-lactamase in Gram-negative bacteria that efficiently catalyzes the hydrolysis of penicillins and early cephalosporins but not oxyimino-cephalosporins. A previous random mutagenesis study identified a W165Y/E166Y/P167G triple mutant that displays greatly altered substrate specificity with increased activity for the oxyimino-cephalosporin, ceftazidime, and decreased activity toward all other β-lactams tested. Surprisingly, this mutant lacks the conserved Glu-166 residue critical for enzyme function. Ceftazidime contains a large, bulky side chain that does not fit optimally in the wild-type TEM-1 active site. Therefore, it was hypothesized that the substitutions in the mutant expand the binding site in the enzyme. To investigate structural changes and address whether there is an enlargement in the active site, the crystal structure of the triple mutant was solved to 1.44 Å. The structure reveals a large conformational change of the active site Ω-loop structure to create additional space for the ceftazidime side chain. The position of the hydroxyl group of Tyr-166 and an observed shift in the pH profile of the triple mutant suggests that Tyr-166 participates in the hydrolytic mechanism of the enzyme. These findings indicate that the highly conserved Glu-166 residue can be substituted in the mechanism of serine β-lactamases. The results reveal that the robustness of the overall β-lactamase fold coupled with the plasticity of an active site loop facilitates the evolution of enzyme specificity and mechanism.     

A Proteomic Strategy Identifies Lysine Methylation of Splicing Factor snRNP70 by the SETMAR Enzyme

The lysine methyltransferase (KMT) SETMAR is implicated in the response to and repair of DNA damage, but its molecular function is not clear. SETMAR has been associated with dimethylation of histone H3 lysine 36 (H3K36) at sites of DNA damage. However, SETMAR does not methylate H3K36 in vitro. This and the observation that SETMAR is not active on nucleosomes suggest that H3K36 methylation is not a physiologically relevant activity. To identify potential non-histone substrates, we utilized a strategy on the basis of quantitative proteomic analysis of methylated lysine. Our approach identified lysine 130 of the mRNA splicing factor snRNP70 as a SETMAR substrate in vitro, and we show that the enzyme primarily generates monomethylation at this position. Furthermore, we show that SETMAR methylates snRNP70 Lys-130 in cells. Because snRNP70 is a key early regulator of 5′ splice site selection, our results suggest a model in which methylation of snRNP70 by SETMAR regulates constitutive and/or alternative splicing. In addition, the proteomic strategy described here is broadly applicable and is a promising route for large-scale mapping of KMT substrates.