Inhibition of yeast ribosomal stalk phosphorylation by Cu-Zn superoxide dismutase

Reversible phosphorylation of acidic ribosomal proteins of Saccharomyces cerevisiae is an important mechanism, regulating the number of active ribosomes. The key role in regulation of this process is played by specific, second messenger-independent protein kinases. A new protein-inhibitor regulating activity of PK60S kinase has been purified from yeast extracts and characterised. Peptide mass fingerprinting (PMF) and amino-acid sequence analysis by Post Source Decay (PSD) have identified the inhibitor as a Cu-Zn superoxide dismutase (SOD). Inhibition by SOD is competitive with respect to protein substrates-P proteins and 80S ribosome-with K(i) values of 3.7 microM for P2A protein and 0.6 microM for 80S ribosomes. A close correlation was found between the state of phosphorylation of P proteins in diauxic shift and logarithmic growth yeast cells and activity of SOD. The possible mechanism of regulation of PK60S activity, and participation of SOD protein in regulation of 80S-ribosome activity in stress conditions, is discussed.     

Genetic and physical maps of jerker (Espn(je)) on mouse chromosome 4

The jerker mutation causes degeneration of cochlea and vestibular sensory hair cells in mice. A frame-shift mutation in the actin bundling gene Espin (Espn) leads to hair bundle defects by disrupting the actin filament assembly in stereocilia. Previously, jerker was mapped to distal mouse chromosome 4. Here, analyzing 2536 informative meioses derived from two intersubspecific intercrosses, we localize jerker to a 0.51+/-0.14cM interval on chromosome 4. The following order and distances of genes and markers were determined: D4Mit180-0.44+/-0.13cM-Hes2, Espn(je)-0.08+/-0.06cM-D4Mit356-0.28+/-0.1cM-D4Mit208. A 300kb physical bacterial artificial chromosome (BAC) contig was generated containing the Espn(je) locus. The human homologous region maps to 1p36.31. We present a detailed high-resolution genetic and physical map of markers located at distal chromosome 4 and demonstrate concordance of Espn with jerker.     

Improved simulation of NOESY spectra by RELAX-JT2 including effects of J-coupling, transverse relaxation and chemical shift anisotropy

RELAX-JT2 is an extension of RELAX, a program for the simulation of 1H 2D NOESY spectra and (15)N or (13)C edited 3D NOESY-HSQC spectra of biological macromolecules. In addition to the already existing NOE-simulation it allows the proper simulation of line shapes by the integrated calculation of T(2) times and multiplet structures caused by J-couplings. Additionally the effects of relaxation mediated by chemical shift anisotropy are taken into account. The new routines have been implemented in the program AUREMOL, which aims at the automated NMR structure determination of proteins in solution. For a manual or automatic assignment of experimental spectra that is based on the comparison with the corresponding simulated spectra, the additional line shape information now available is a valuable aid. The new features have been successfully tested with the histidine-containing phosphocarrier protein HPr from Staphylococcus carnosus.     

Effects of proteinase inhibitors on fertilization in sea lamprey (Petromyzon marinus)

A search for alternative sterilants in parasitic fish encouraged us to explore the usefulness of proteinase inhibitors for this purpose. Fertilization in sea lamprey species (Petromyzon marinus L.) was inhibited by chymotrypsin and trypsin inhibitors 4'-acetamidophenyl 4-guanidinobenzoate (AGB), chymostatin, tosyl-L-lysine chloromethyl ketone (TLCK), and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) when these substances were added into a fertilization medium at the time of fertilization. Preincubation of eggs before fertilization with 100 microM TPCK, but not TLCK, resulted in inhibition of fertilization. Conversely, preincubation of spermatozoa with TLCK, but not TPCK, produced inhibition of fertilization. These data suggest the involvement of the chymotrypsin-like activity of eggs and trypsin-like activity of spermatozoa in fertilization. However, enzymes present in sperm suspensions were able to hydrolyze a chymotrypsin substrate N-glutaryl-L-phenylalanine-p-nitroanilide (GPNA) but not trypsin substrate N-alpha-benzoyl-DL-arginine-p-nitroanilide (BAPNA). The nature of this activity can be characterized as serine protease and our results indicate the involvement of serine proteinases in the fertilization of sea lamprey.     

A neuroeconomics approach to inferring utility functions in sensorimotor control

Making choices is a fundamental aspect of human life. For over a century experimental economists have characterized the decisions people make based on the concept of a utility function. This function increases with increasing desirability of the outcome, and people are assumed to make decisions so as to maximize utility. When utility depends on several variables, indifference curves arise that represent outcomes with identical utility that are therefore equally desirable. Whereas in economics utility is studied in terms of goods and services, the sensorimotor system may also have utility functions defining the desirability of various outcomes. Here, we investigate the indifference curves when subjects experience forces of varying magnitude and duration. Using a two-alternative forced-choice paradigm, in which subjects chose between different magnitude–duration profiles, we inferred the indifference curves and the utility function. Such a utility function defines, for example, whether subjects prefer to lift a 4-kg weight for 30 s or a 1-kg weight for a minute. The measured utility function depends nonlinearly on the force magnitude and duration and was remarkably conserved across subjects. This suggests that the utility function, a central concept in economics, may be applicable to the study of sensorimotor control.     

Alpha-tocopherol downregulates gulonolactone oxidase activity in sturgeon

Gulonolactone oxidase (GLO) is the enzyme responsible for the last step of ascorbic acid biosynthesis. The aim of this study was to investigate the effect of dietary alpha-tocopherol and ascorbic acid on GLO activity in a lower vertebrate, the white sturgeon (Acipenser transmontanus). Both alpha-tocopherol and ascorbic acid modulated renal GLO activity. The increase of dietary levels of alpha-tocopherol and/or ascorbic acid significantly raised the liver concentrations of these two antioxidants and concomitantly lowered kidney's GLO activity. The results suggest that the enzyme of ascorbic acid synthetic pathway responded to the animal's antioxidant status and that its activity was downregulated by alpha-tocopherol. This is the first record of alpha-tocopherol being involved in the regulation of ascorbic acid synthesis. This new observation may provide a hypothesis for the evolutionary loss of GLO expression in teleost fishes.     

Structural basis for the dual thymidine and thymidylate kinase activity of herpes thymidine kinases

Crystal structures of equine herpesvirus type-4 thymidine kinase (EHV4-TK) in complex with (i). thymidine and ADP, (ii). thymidine and SO(4) and the bisubstrate analogs, (iii). TP(4)A, and (iv). TP(5)A have been solved. Additionally, the structure of herpes simplex virus type-1 thymidine kinase (HSV1-TK) in complex with TP(5)A has been determined. These are the first structures of nucleoside kinases revealing conformational transitions upon binding of bisubstrate analogs. The structural basis for the dual thymidine and thymidylate kinase activity of these TKs is elucidated. While the active sites of HSV1-TK and EHV4-TK resemble one another, notable differences are observed in the Lid regions and in the way the enzymes bind the base of the phosphoryl-acceptor. The latter difference could partly explain the higher activity of EHV4-TK toward the prodrug ganciclovir.     

Flow fields generated by peristaltic reflex in isolated guinea pig ileum: impact of contraction depth and shoulders

The guinea pig ileum responds to distension with characteristic wall movements, luminal pressure gradients, and outflow (the peristaltic reflex). To date, little is known about whether the peristaltic reflex generates flow events other than laminar flow. Here we used a numerical method to solve for the flow generated by moving walls to assess occlusive contractions (case 1), nonocclusive contractions (case 2), and contractions with steep shoulders (case 3) for which visual parameters of wall movements are published. We found that all three contraction cases produced pressure differentials across the coapting segment, downstream and reverse flow, and vortical flow patterns that redistributed particles and mixed liquids. Contractions generated pressures and shear stresses, particularly along the moving section of the wall. The nonocclusive contraction was much less effective than the occlusive contraction with the steep shoulders; the occlusive contraction with flat shoulders had an intermediate effect. Our analysis shows that even peristaltic contractions produce not only laminar flow but also many flow events likely to promote digestion and absorption. The visual patterns of contractions impact the patterns of luminal flow, and precise definition of wall movements is critical to quantify the fluid mechanical consequences of intestinal contractions.