Structure and activity cyclase activated of OK-GC: A kidney receptor-guanylate cyclase activated by guanylin peptides

Uroguanylin, guanylin, and lymphoguanylin are small peptides that activate renal and intestinal receptor guanylate cyclases (GC). They are structurally similar to bacterial heat-stable enterotoxins (ST) that cause secretory diarrhea. Uroguanylin, guanylin, and ST elicit natriuresis, kaliuresis, and diuresis by direct actions on kidney GC receptors. A 3,762-bp cDNA characterizing a uroguanylin/guanylin/ST receptor was isolated from opossum kidney (OK) cell RNA/cDNA. This kidney cDNA (OK-GC) encodes a mature protein containing 1,049 residues sharing 72.4�75.8% identity with rat, human, and porcine forms of intestinal GC-C receptors. COS or HEK-293 cells expressing OK-GC receptor protein were activated by uroguanylin, guanylin, or ST13 peptides. The 3.8-kb OK-GC mRNA transcript is most abundant in the kidney cortex and intestinal mucosa, with lower mRNA levels observed in urinary bladder, adrenal gland, and myocardium and with no detectable transcripts in skin or stomach mucosa. We propose that OK-GC receptor GC participates in a renal mechanism of action for uroguanylin and/or guanylin in the physiological regulation of urinary sodium, potassium, and water excretion. This renal tubular receptor GC may be a target for circulating uroguanylin in an endocrine link between the intestine and kidney and/or participate in an intrarenal paracrine mechanism for regulation of kidney function via the intracellular second messenger, cGMP.

The beta-glucoside genes of Klebsiella aerogenes: conservation and divergence in relation to the cryptic bgl genes of Escherichia coli

The ability to metabolize aromatic beta-glucosides such as salicin and arbutin varies among members of the Enterobacteriaceae. The ability of Escherichia coli to degrade salicin and arbutin appears to be cryptic, subject to activation of the bgl genes, whereas many members of the Klebsiella genus can metabolize these sugars. We have examined the genetic basis for beta-glucoside utilization in Klebsiella aerogenes. The Klebsiella equivalents of bglG, bglB and bglR have been cloned using the genome sequence database of Klebsiella pneumoniae. Nucleotide sequencing shows that the K. aerogenes bgl genes show substantial similarities to the E. coli counterparts. The K. aerogenes bgl genes in multiple copies can also complement E. coli mutants deficient in bglG encoding the antiterminator and bglB encoding the phospho-beta-glucosidase, suggesting that they are functional homologues. The regulatory region bglR of K aerogenes shows a high degree of similarity of the sequences involved in BglG-mediated regulation. Interestingly, the regions corresponding to the negative elements present in the E. coli regulatory region show substantial divergence in K aerogenes. The possible evolutionary implications of the results are discussed. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.v. All rights reserved.

Structure and nucleotide specificity of Staphylococcus aureus dihydrodipicolinate reductase (DapB)

Lysine biosynthesis proceeds by the nucleotide-dependent reduction of dihydrodipicolinate (DHDP) to tetrahydrodipicolinate (THDP) by dihydrodipicolinate reductase (DHDPR). The S. aureus DHDPR structure reveals different conformational states of this enzyme even in the absence of a substrate or nucleotide-cofactor. Despite lacking a conserved basic residue essential for NADPH interaction, S. aureus DHDPR differs from other homologues as NADPH is a more preferred co-factor than NADH. The structure provides a rationale-Lys35 compensates for the co-factor site mutation. These observations are significant for bi-ligand inhibitor design that relies on ligand-induced conformational changes as well as co-factor specificity for this important drug target. Structured summary of protein interactions: DHDPR binds to DHDPR by molecular sieving (View interaction). DHDPR binds to DHDPR by dynamic light scattering (View interaction). DHDPR binds to DHDPR by X-ray crystallography (View interaction). (C) 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Insights into differential modulation of receptor function by hinge region using novel agonistic lutropin receptor and inverse agonistic thyrotropin receptor antibodies

We report two antibodies, scFv 13B1 and MAb PD1.37, against the hinge regions of LHR and TSHR, respectively, which have similar epitopes but different effects on receptor function. While neither of them affected hormone binding, with marginal effects on hormone response, scFv 13B1 stimulated LHR in a dose-dependent manner, whereas MAb PD1.37 acted as an inverse agonist of TSHR. Moreover, PD1.37 could decrease the basal activity of hinge region CAMs, but had varied effects on those present in ECLs, whereas 13B1 was refractory to any CAMs in LHR. Using truncation mutants and peptide phage display, we compared the differential roles of the hinge region cysteine box-2/3 as well as the exoloops in the activation of these two homologus receptors. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Redox modification of Akt mediated by the dopaminergic neurotoxin MPTP, in mouse midbrain, leads to down-regulation of pAkt

Impairment of Akt phosphorylation, a critical survival signal, has been implicated in the degeneration of dopaminergic neurons in Parkinson's disease. However, the mechanism underlying pAkt loss is unclear. In the current study, we demonstrate pAkt loss in ventral midbrain of mice treated with dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), when compared to ventral midbrain of control mice treated with vehicle alone. Thiol residues of the critical cysteines in Akt are oxidized to a greater degree in mice treated with MPTP, which is reflected as a 40% loss of reduced Akt. Association of oxidatively modified Akt with the phosphatase PP2A, which can lead to enhanced dephosphorylation of pAkt, was significantly stronger after MPTP treatment. Maintaining the protein thiol homeostasis by thiol antioxidants prevented loss of reduced Akt, decreased association with PP2A, and maintained pAkt levels. Overexpression of glutaredoxin, a protein disulfide oxidoreductase, in human primary neurons helped sustain reduced state of Akt and abolished MPP+-mediated pAkt loss. We demonstrate for the first time the selective loss of Akt activity, in vivo, due to oxidative modification of Akt and provide mechanistic insight into oxidative stress-induced down-regulation of cell survival pathway in mouse midbrain following exposure to MPTP.-Durgadoss, L., Nidadavolu, P., Khader Valli, R., Saeed, U., Mishra, M., Seth, P., Ravindranath, R. Redox modification of Akt mediated by the dopaminergic neurotoxin MPTP, in mouse midbrain, leads to down-regulation of pAkt. FASEB J. 26, 1473-1483 (2012). www.fasebj.org

Regulation of lipid biosynthesis by phosphatidylinositol-specific phospholipase C through the transcriptional repression of upstream activating sequence inositol containing genes

The regulation of phospholipid biosynthesis in Saccharomyces cerevisiae through cis-acting upstream activating sequence inositol (UAS(ino)) and trans-acting elements, such as the INO2-INO4 complex and OPI1 by inositol supplementation in growth is thoroughly studied. In this study, we provide evidence for the regulation of lipid biosynthesis by phosphatidylinositol-specific phospholipase C (PLC) through UAS(ino) and the trans-acting elements. Gene expression analysis and radiolabelling experiments demonstrated that the overexpression of rice PLC in yeast cells altered phospholipid biosynthesis at the levels of transcriptional and enzyme activity. This is the first report implicating PLC in the direct regulation of lipid biosynthesis. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Performance of inherently compensated flat pad aerostatic bearings subject to dynamic perturbation forces

The importance of air bearing design is growing in engineering. As the trend to precision and ultra precision manufacture gains pace and the drive to higher quality and more reliable products continues, the advantages which can be gained from applying aerostatic bearings to machine tools, instrumentation and test rigs is becoming more apparent. The inlet restrictor design is significant for air bearings because it affects the static and dynamic performance of the air bearing. For instance pocketed orifice bearings give higher load capacity as compared to inherently compensated orifice type bearings, however inherently compensated orifices, also known as laminar flow restrictors are known to give highly stable air bearing systems (less prone to pneumatic hammer) as compared to pocketed orifice air bearing systems. However, they are not commonly used because of the difficulties encountered in manufacturing and assembly of the orifice designs. This paper aims to analyse the static and dynamic characteristics of inherently compensated orifice based flat pad air bearing system. Based on Reynolds equation and mass conservation equation for incompressible flow, the steady state characteristics are studied while the dynamic state characteristics are performed in a similar manner however, using the above equations for compressible flow. Steady state experiments were also performed for a single orifice air bearing and the results are compared to that obtained from theoretical studies. A technique to ease the assembly of orifices with the air bearing plate has also been discussed so as to make the manufacturing of the inherently compensated bearings more commercially viable. (c) 2012 Elsevier Inc. All rights reserved.

The multiple and enigmatic roles of guanylyl cyclase C in intestinal homeostasis

Guanylyl cyclase C (GC-C) is predominantly expressed in intestinal epithelial cells and serves as the receptor for the gastrointestinal hormones guanylin and uroguanylin, and the heat-stable enterotoxin, the causative agent for Travellers' Diarrhea. Activation of GC-C results in an increase in intracellular levels of cGMP, which can regulate fluid and ion secretion, colon cell proliferation, and the gut immune system. This review highlights recent findings arising from studies in the GC-C knockout mouse, along with enigmatic results obtained from the first descriptions of human disease caused by mutations in the GC-C gene. We provide some insight into these new findings and comment on areas of future study, which may enhance our knowledge of this evolutionarily conserved receptor and signaling system. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.

The evolution of complexity in social organization-A model using dominance-subordinate behavior in two social wasp species

Dominance and subordinate behaviors are important ingredients in the social organizations of group living animals. Behavioral observations on the two eusocial species Ropalidia marginata and Ropalidia cyathiformis suggest varying complexities in their social systems. The queen of R. cyathiformis is an aggressive individual who usually holds the top position in the dominance hierarchy although she does not necessarily show the maximum number of acts of dominance, while the R. marginata queen rarely shows aggression and usually does not hold the top position in the dominance hierarchy of her colony. In R. marginata, more workers are involved in dominance-subordinate interactions as compared to R. cyathiformis. These differences are reflected in the distribution of dominance-subordinate interactions among the hierarchically ranked individuals in both the species. The percentage of dominance interactions decreases gradually with hierarchical ranks in R. marginata while in R. cyathiformis it first increases and then decreases. We use an agent-based model to investigate the underlying mechanism that could give rise to the observed patterns for both the species. The model assumes, besides some non-interacting individuals, the interaction probabilities of the agents depend on their pre-differentiated winning abilities. Our simulations show that if the queen takes up a strategy of being involved in a moderate number of dominance interactions, one could get the pattern similar to R. cyathiformis, while taking up the strategy of very low interactions by the queen could lead to the pattern of R. marginata. We infer that both the species follow a common interaction pattern, while the differences in their social organization are due to the slight changes in queen as well as worker strategies. These changes in strategies are expected to accompany the evolution of more complex societies from simpler ones.

Socio-cultural protection of endemic trees in humanised landscape

Culturally protected forest patches or sacred groves have been the integral part of many traditional societies. This age old tradition is a classic instance of community driven nature conservation sheltering native biodiversity and supporting various ecosystem functions particularly hydrology. The current work in Central Western Ghats of Karnataka, India, highlights that even small sacred groves amidst humanised landscapes serve as tiny islands of biodiversity, especially of rare and endemic species. Temporal analysis of landuse dynamics reveals the changing pattern of the studied landscape. There is fast reduction of forest cover (15.14-11.02 %) in last 20 years to meet up the demand of agricultural land and plantation programs. A thorough survey and assessment of woody endemic species distribution in the 25 km(2) study area documented presence of 19 endemic species. The distribution of these species is highly skewed towards the culturally protected patches in comparison to other land use elements. It is found that, among the 19 woody endemic species, those with greater ecological amplitude are widely distributed in the studied landscape in groves as well as other land use forms whereas, natural population of the sensitive endemics are very much restricted in the sacred grove fragments. The recent degradation in the sacred grove system is perhaps, due to weakening of traditional belief systems and associated laxity in grove protection leading to biotic disturbances. Revitalisation of traditional practices related to conservation of sacred groves can go a long way in strengthening natural ecological systems of fragile humid tropical landscape.

Crystal structure of a putative aspartic proteinase domain of the Mycobacterium tuberculosis cell surface antigen PE_PGRS16

We report the crystal structure of the first prokaryotic aspartic proteinase-like domain identified in the genome of Mycobacterium tuberculosis. A search in the genomes of Mycobacterium species showed that the C-terminal domains of some of the PE family proteins contain two classic DT/SG motifs of aspartic proteinases with a low overall sequence similarity to HIV proteinase. The three-dimensional structure of one of them, Rv0977 (PE_PGRS16) of M. tuberculosis revealed the characteristic pepsinf-old and catalytic site architecture. However, the active site was completely blocked by the N-terminal His-tag. Surprisingly, the enzyme was found to be inactive even after the removal of the N-terminal His-tag. A comparison of the structure with pepsins showed significant differences in the critical substrate binding residues and in the flap tyrosine conformation that could contribute to the lack of proteolytic activity of Rv0977. (C) 2013 The Authors. Published by Elsevier B.V. on behalf of Federation of European Biochemical Societies. All rights reserved.

Functional roles of N-terminal and C-terminal domains in the overall activity of a novel single-stranded DNA binding protein of Deinococcus radiodurans

Single-stranded DNA binding protein (Ssb) of Deinococcus radiodurans comprises N- and C-terminal oligonucleotide/oligosaccharide binding (OB) folds connected by a beta hairpin connector. To assign functional roles to the individual OB folds, we generated three Ssb variants: Ssb(N) (N-terminal without connector), Ssb(NC) (N-terminal with connector) and Ssb(C) (C-terminal), each harboring one OB fold. Both Ssb(N) and Ssb(NC) displayed weak single-stranded DNA (ssDNA) binding activity, compared to the full-length Ssb (Ssb(FL)). The level of ssDNA binding activity displayed by SsbC was intermediate between Ssb(FL) and Ssb(N). Ssb(C) and Ssb(FL) predominantly existed as homo-dimers while Ssb(NC)/Ssb(N) formed different oligomeric forms. In vitro, Ssb(NC) or Ssb(N) formed a binary complex with Ssb(C) that displayed enhanced ssDNA binding activity. Unlike Ssb(FL), Ssb variants were able to differentially modulate topoisomerase-I activity, but failed to stimulate Deinococcal RecA-promoted DNA strand exchange. The results suggest that the C-terminal OB fold is primarily responsible for ssDNA binding. The N-terminal OB fold binds weakly to ssDNA but is involved in multimerization. (C) 2015 The Authors. Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies. This is an open access article under the CC BY-NC-ND license.

De la teoría al análisis de los sistemas-mundo : consideraciones sobre la interacción entre Egipto, Kerma y Biblos (c. 1985-1640 a.C.)

Resumen: Este trabajo aborda la posibilidad de analizar las relaciones entre diferentes sociedades del noreste de África y el Levante a través del análisis de los sistemas-mundo c. 1985–1640 a.C.