Effect of alanine versus glycine in alpha-helices on protein stability.

The rational design of proteins requires knowledge of the helix-forming propensities (s-values) of the different amino acids. There is, however, considerable controversy about the relative values for alanine and glycine. We find from experiments on mutants of barnase that the relative effect of Ala versus Gly on helix stability depends crucially on the position in the helix (whether they are at the ends (caps) or are internal) and the context (the influence of their neighbours). Glycine is greatly preferred at the N and C caps. At internal positions, Ala stabilizes the helix relative to Gly by 0.4 to 2 kcal mol-1. The variation results from a combination of burial of hydrophobic surface on folding and interference with hydrogen bonding of the protein with solvent. There is a good empirical correlation between the relative stabilizing effects of Ala and Gly with the total change in solvent-accessible hydrophobic surface area of the folded protein on mutation of Gly to Ala. It is not valid to assign to each amino acid a unique s-value that is generally applicable to all positions in all helices in all proteins.     

Critical role for the p110alpha phosphoinositide-3-OH kinase in growth and metabolic regulation

The eight catalytic subunits of the mammalian phosphoinositide-3-OH kinase (PI(3)K) family form the backbone of an evolutionarily conserved signalling pathway; however, the roles of most PI(3)K isoforms in organismal physiology and disease are unknown. To delineate the role of p110alpha, a ubiquitously expressed PI(3)K involved in tyrosine kinase and Ras signalling, here we generated mice carrying a knockin mutation (D933A) that abrogates p110alpha kinase activity. Homozygosity for this kinase-dead p110alpha led to embryonic lethality. Mice heterozygous for this mutation were viable and fertile, but displayed severely blunted signalling via insulin-receptor substrate (IRS) proteins, key mediators of insulin, insulin-like growth factor-1 and leptin action. Defective responsiveness to these hormones led to reduced somatic growth, hyperinsulinaemia, glucose intolerance, hyperphagia and increased adiposity in mice heterozygous for the D933A mutation. This signalling function of p110alpha derives from its highly selective recruitment and activation to IRS signalling complexes compared to p110beta, the other broadly expressed PI(3)K isoform, which did not contribute to IRS-associated PI(3)K activity. p110alpha was the principal IRS-associated PI(3)K in cancer cell lines. These findings demonstrate a critical role for p110alpha in growth factor and metabolic signalling and also suggest an explanation for selective mutation or overexpression of p110alpha in a variety of cancers.     

Effect of insulin in vivo on the synthesis of free fatty acids (FFA) in chicken heart and skeletal muscle

Summary The effect of insulin on the synthesis of free fatty acids from glucose in the skeletal and heart muscles of chicken is examined. 10 min after glucose-(U-¹⁴C) administration, labeled free fatty acids (FFA) appeared in both skeletal and heart muscles. 0.75 IU of insulin kg^–1 b. wt significantly increased the labeled FFA at the 30, 60 and 120 min intervals, with a maximum at 60 min.     

Validating Policy‐Induced Economic Change Using Sequential General Equilibrium SAMs

We present a novel sequential approach that explores the capacity of Computable general equilibrium (CGE) models to track down policy‐induced economic changes and their ability to generate contrastable data. We use an empirical Social accounting matrix (SAM) of the region of Andalusia, in the south of Spain, to construct an initial CGE model. This model is then perturbed with a set of policy shocks related to EU Structural Funds invested into Andalusia. These shocks are accompanied by some parameter adjustments that pick up the main external changes not explained by the model. We generate a sequence of model‐produced virtual SAMs. We then compare the last virtual SAM in the sequence with a new available empirical SAM. This allows us to check relatedness, for the same year, between the model produced and the empirical SAMs. The results show a good fit to the empirical data, providing further support to the CGE modelling tool. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of acute administration of triiodothyronine in chicken. Liver glycogen depletion and amino acid incorporation to proteins

Summary Single injections of thyroid hormone (T₃) produce liver glycogen depletion in chickens. This effect cannot be suppressed by protein synthesis inhibitors and is previous to the hormone-induced increase in protein synthesis.     

Variation in genome-wide mutation rates within and between human families

J.B.S. Haldane proposed in 1947 that the male germline may be more mutagenic than the female germline. Diverse studies have supported Haldane's contention of a higher average mutation rate in the male germline in a variety of mammals, including humans. Here we present, to our knowledge, the first direct comparative analysis of male and female germline mutation rates from the complete genome sequences of two parent-offspring trios. Through extensive validation, we identified 49 and 35 germline de novo mutations (DNMs) in two trio offspring, as well as 1,586 non-germline DNMs arising either somatically or in the cell lines from which the DNA was derived. Most strikingly, in one family, we observed that 92% of germline DNMs were from the paternal germline, whereas, in contrast, in the other family, 64% of DNMs were from the maternal germline. These observations suggest considerable variation in mutation rates within and between families.     

EphB-ephrin-B interactions suppress colorectal cancer progression by compartmentalizing tumor cells

The genes encoding tyrosine kinase receptors EphB2 and EphB3 are beta-catenin and Tcf4 target genes in colorectal cancer (CRC) and in normal intestinal cells. In the intestinal epithelium, EphB signaling controls the positioning of cell types along the crypt-villus axis. In CRC, EphB activity suppresses tumor progression beyond the earliest stages. Here we show that EphB receptors compartmentalize the expansion of CRC cells through a mechanism dependent on E-cadherin-mediated adhesion. We demonstrate that EphB-mediated compartmentalization restricts the spreading of EphB-expressing tumor cells into ephrin-B1-positive territories in vitro and in vivo. Our results indicate that CRC cells must silence EphB expression to avoid repulsive interactions imposed by normal ephrin-B1-expressing intestinal cells at the onset of tumorigenesis.     

Flavodoxins: sequence, folding, binding, function and beyond

Flavodoxins are electron-transfer proteins involved in a variety of photosynthetic and non-photosynthetic reactions in bacteria, whereas, in eukaryotes, a descendant of the flavodoxin gene helps build multidomain proteins. The redox activity of flavodoxin derives from its bound flavin mononucleotide cofactor (FMN), whose intrinsic properties are profoundly modified by the host apoprotein. This review covers the very exciting last decade of flavodoxin research, in which the folding pathway, the structure and stability of the apoprotein, the mechanism of FMN recognition, the interactions that stabilize the functional complex and tailor the redox potentials, and many details of the binding and electron transfer to partner proteins have been revealed. The next decade should witness an even deeper understanding of the flavodoxin molecule and a greater comprehension of its many physiological roles. The fact that flavodoxin is essential for the survival of some human pathogens could make it a drug target on its own. Received 26 October 2005; received after revision 20 November 2005; accepted 14 December 2005     

Insights or forecasts? An evaluation of a computable general equilibrium model of spain

Computable general equilibrium (CGE) models are widely used as an advanced tool to evaluate alternative economic strategies and policy measures. These models are well rooted in solid economic theory, yet a crucial question is hardly asked: how well do these models perform? We address this question by comparing the economic performance of the Spanish economy in 1988 with the simulation results drawn from a CGE model calibrated with a 1987 Social Accounting Matrix. The values of endogenous variables used in the comparison are the equilibrium values provided by the model after updating the values of exogenous variables such as labour and capital endowments, real exports and effective nominal exchange rates with the European Community and the rest of the world, real government expenditures, and various tax rates, government subsidies, and transfers. The comparison shows that the model captures adequately the major developments that occurred in the Spanish economy in 1988. This result increases our confidence in the quantitative estimates derived from the model in the usual simulation exercises.