Having good spatial skills strongly predicts achievement and attainment in science, technology, engineering, and mathematics fields (e.g., Shea, Lubinski, & Benbow, 2001; Wai, Lubinski, & Benbow, 2009).
View Article and Find Full Text PDFWe apply the item-order theory of list composition effects in free recall to the orthographic distinctiveness effect. The item-order account assumes that orthographically distinct items advantage item-specific encoding in both mixed and pure lists, but at the expense of exploiting relational information present in the list. Experiment 1 replicated the typical free recall advantage of orthographically distinct items in mixed lists and the elimination of that advantage in pure lists.
View Article and Find Full Text PDFIIAGlc, a component of the glucose-specific phosphoenolpyruvate:phosphotransferase system (PTS) of Escherichia coli, is important in regulating carbohydrate metabolism. In Glc uptake, the phosphotransfer sequence is: phosphoenolpyruvate --> Enzyme I --> HPr --> IIAGlc --> IICBGlc --> Glc. (HPr is the first phosphocarrier protein of the PTS.
View Article and Find Full Text PDFThe complete time-resolved fluorescence of tryptophan in the proteins monellin and IIA(Glc) has been investigated, using both an upconversion spectrophotofluorometer with 150 fs time resolution and a time-correlated single photon counting apparatus on the 100 ps to 20 ns time scale. In monellin, the fluorescence decay displays multiexponential character with decay times of 1.2 and 16 ps, and 0.
View Article and Find Full Text PDFDuring translocation across the cytoplasmic membrane of Escherichia coli, glucose is phosphorylated by phospho-IIA(Glc) and Enzyme IICB(Glc), the last two proteins in the phosphotransfer sequence of the phosphoenolpyruvate:glucose phosphotransferase system. Transient state (rapid quench) methods were used to determine the second order rate constants that describe the phosphotransfer reactions (phospho-IIA(Glc) to IICB(Glc) to Glc) and also the second order rate constants for the transfer from phospho-IIA(Glc) to molecularly cloned IIB(Glc), the soluble, cytoplasmic domain of IICB(Glc). The rate constants for the forward and reverse phosphotransfer reactions between IIA(Glc) and IICB(Glc) were 3.
View Article and Find Full Text PDFThe first two reactions in the phosphotransfer sequence of bacterial phosphoenolpyruvate:glycose phosphotransferase systems are the autophosphorylation of Enzyme I by phosphoenolpyruvate followed by the transfer of the phospho group to the low-molecular weight protein, HPr. Transient state kinetic methods were used to estimate the second-order rate constants for both phosphotransfer reactions. These measurements support previous conclusions that only the dimer of Enzyme I, EI2, is autophosphorylated, and that the rate of formation of dimer is slow compared to the rate of its phosphorylation.
View Article and Find Full Text PDFReverse genetics is used to evaluate the roles in vivo of allosteric regulation of Escherichia coli glycerol kinase by the glucose-specific phosphocarrier of the phosphoenolpyruvate:glycose phosphotransferase system, IIA(Glc) (formerly known as III(glc)), and by fructose 1,6-bisphosphate. Roles have been postulated for these allosteric effectors in glucose control of both glycerol utilization and expression of the glpK gene. Genetics methods based on homologous recombination are used to place glpK alleles with known specific mutations into the chromosomal context of the glpK gene in three different genetic backgrounds.
View Article and Find Full Text PDFThe kinetic parameters in vitro of the components of the phosphoenolpyruvate:glycose phosphotransferase system (PTS) in enteric bacteria were collected. To address the issue of whether the behavior in vivo of the PTS can be understood in terms of these enzyme kinetics, a detailed kinetic model was constructed. Each overall phosphotransfer reaction was separated into two elementary reactions, the first entailing association of the phosphoryl donor and acceptor into a complex and the second entailing dissociation of the complex into dephosphorylated donor and phosphorylated acceptor.
View Article and Find Full Text PDFIn Escherichia coli, inducer exclusion is one mechanism by which glucose prevents unnecessary expression of genes needed for metabolism of other sugars. The basis for this mechanism is binding of the unphosphorylated form of the glucose-specific phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system, IIAGlc (also known as IIIGlc), to a variety of target proteins to prevent uptake or synthesis of the inducer. One of these target proteins is glycerol kinase (EC 2.
View Article and Find Full Text PDFIn Escherichia coli, the glucose-specific phosphocarrier protein of the phosphotransferase system (PTS), IIAGlc (IIIGlc in older literature), is also the central regulatory protein of the PTS. Depending upon its state of phosphorylation, IIAGlc binds to a number of different proteins that display no apparent sequence homology. Previous structural studies suggested that nonspecific hydrophobic interactions, specific salt bridges, and an intermolecular Zn(II) binding site contribute to the wide latitude in IIAGlc binding sites.
View Article and Find Full Text PDFIIIGlc (also called IIAGlc), a major signal-transducing protein in Escherichia coli, is also a phosphorylcarrier in glucose uptake. The crystal and NMR structures of IIIGlc show that His90, the phosphoryl acceptor, adjoins His75 in the active site. Glutamine was substituted for His-, giving H75QIIIGlc and H90QIIIGlc, respectively (Presper, K.
View Article and Find Full Text PDFThe bacterial phosphoenolpyruvate:glycose phosphotransferase system (PTS) plays a central role in catabolizing many sugars; regulation is effected by phosphorylation of PTS proteins. In Escherichia coli, the phosphoryltransfer sequence for glucose uptake is: PEP --> Enzyme I(His191) --> HPr(His15) --> IIIGlc(His90) --> IIGlc(Cys421) --> glucose. A rapid quench method has now been developed for determining the rate and equilibrium constants of these reactions.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
April 1994
A central question in molecular biology concerns the means by which a regulatory protein recognizes different targets. IIIGlc, the glucose-specific phosphocarrier protein of the bacterial phosphotransferase system, is also the central regulatory element of the PTS. Binding of unphosphorylated IIIGlc inhibits several non-PTS proteins, but there is little or no sequence similarity between IIIGlc binding sites on different target proteins.
View Article and Find Full Text PDFIIIGlc is an 18.1-kDa signal-transducing phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system from Escherichia coli. The 1H, 15N, and 13C histidine ring NMR signals of both the phosphorylated and unphosphorylated forms of IIIGlc have been assigned using two-dimensional 1H-15N and 1H-13C heteronuclear multiple-quantum coherence (HMQC) experiments and a two-dimensional 13C-13C-1H correlation spectroscopy via JCC coupling experiment.
View Article and Find Full Text PDFThe phosphocarrier protein IIIGlc is an integral component of the bacterial phosphotransferase (PTS) system. Unphosphorylated IIIGlc inhibits non-PTS carbohydrate transport systems by binding to diverse target proteins. The crystal structure at 2.
View Article and Find Full Text PDFThe 18.1-kDa protein IIIGlc from Escherichia coli acts as both a phosphocarrier protein in the phosphoenolpyruvate:glycose phosphotransferase system (PTS) and as a signal-transducing protein with respect to the uptake of non-PTS sugars. Phosphorylation of IIIGlc at the N epsilon (N3) position of His-90 was effected through a regeneration system that included MgCl2, DTT, excess PEP, and catalytic amounts of Enzyme I and HPr.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
December 1991
The crystal structure of a proteolytically modified form of the Escherichia coli phosphocarrier and signal transducing protein IIIglc has been determined by multiple isomorphous and molecular replacement. The model has been refined to an R-factor of 0.166 for data between 6- and 2.
View Article and Find Full Text PDFIIIGlc is an 18.1-kDa signal-transducing phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system (PTS) of Escherichia coli. Virtually complete (98%) backbone 1H, 15N, and 13C nuclear magnetic resonance (NMR) signal assignments were determined by using a battery of triple-resonance three-dimensional (3D) NMR pulse sequences.
View Article and Find Full Text PDFIIIGlc is a signal-transducing phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system of Escherichia coli. The secondary structure of IIIGlc is determined by heteronuclear (15N, 13C) three-dimensional NMR spectroscopy. Sequential, medium-range, and long-range nuclear Overhauser effects seen in NMR spectra are used to elucidate 11 antiparallel beta-strands and four helical segments.
View Article and Find Full Text PDFThe glucose-specific phosphocarrier protein (IIIGlc) of the bacterial phosphoenolpyruvate:glycose phosphotransferase system (PTS) is a major signal transducer that mediates the intricate interplay among extracellular signals (PTS and non-PTS sugars), cytoplasmic and membrane proteins (PTS and non-PTS transporters), and adenylate cyclase. To further define the central role of IIIGlc in these multiplex signaling mechanisms, we have used site-directed mutagenesis to construct three mutant IIIGlc proteins containing single amino acid changes; Phe-3 was replaced with tryptophan [( Trp3]IIIGlc), and His-75 and the active-site His-90 were replaced with glutamine [( Gln75]IIIGlc and [Gln90]IIIGlc, respectively). [Trp3]IIIGlc resembles the wild-type protein in most properties and should be valuable for spectrophotometric experiments.
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