PROTEINS, AMINO ACIDS AND PEPTIDES as Ions and Dipolar Ions

Cohn, Edwin J.; Edsall, John T.; Kirkwood, John G.; Mueller, H.; Oncley, J. L.; Scatchard, George

doi:10.1097/00000441-194306000-00035

Cited by 475 publications

(143 citation statements)

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“…This would give rise to an electrostatic attraction for anions, and the protein is known to bind anions, including chloride (Stellwagen & Babul, 1975;Taborsky & McCollum, 1979;Osherhoff et al, 1980). Electrostatic interactions would release electrostricted water, which would cause a net rise in volume (Cohn et al, 1934;Cohn & Edsall, 1943). A V is negative, however, so if release of electrostricted water occurs, its effect is masked by another.…”

Section: Resultsmentioning

confidence: 99%

Volume changes of the molten globule transitions of horse heart ferricytochrome c: A thermodynamic cycle

et al. 1995

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Volume changes among the unfolded (U), native (N), and molten globule (MG) conformations of horse heart ferricytochrome c have been measured. U to N (pH 2 to pH 7) was determined in the absence of added salt to be -136 k 5 mL/mol protein. IJ to MG (pH 2, no added salt to pH 2, 0.5 M KCI) yielded + 1 0 0 k 6 mL/mol. MG to N was broken into two steps, N to NCI, at pH 7 by addition of buffered KC1 to buffered protein lacking added salt (NClx = N interacting with an unknown number, X, of chloride ions), and MG to NCl, by jumping MG at pH 2 in 0.5 M KC1 to pH 7 at the same salt concentration. The A V of N to NCI, was -30.9 k 1.4 mL/mol protein, whereas MG to NClx entailed a AVof -235 t-6 mL/mol. Within experimental error, the results add up to zero for a complete thermodynamic cycle. We believe this to be the first volumetric cycle to have been measured for the conformational transitions of a protein. The results are discussed in terms of hydration contributions from deprotonation of the protein, other hydration effects, and the formation and/or enlargement of packing defects in the protein's tertiary structure during the steps of folding.

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Section: Resultsmentioning

confidence: 99%

Volume changes of the molten globule transitions of horse heart ferricytochrome c: A thermodynamic cycle

et al. 1995

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“…The results of all determinations are presented in Table 1. c Determined by using the formula M ϭ 6 Nas/(1 Ϫ vq) (30), where is solvent viscosity, N is Avogadro's number, a is Stokes radius, s is sedimentation coefficient, q is solvent density, and v is partial specific volume (0.73 ml/g) calculated from amino acid composition (10).…”

Section: Discussionmentioning

confidence: 99%

Defect in general priming conferred by linker region mutants of Escherichia coli dnaB

Stordal

Maurer

1996

J Bacteriol

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The dnaB gene of Escherichia coli encodes a bifunctional primase accessory protein/helicase necessary for chromosomal replication. Monomers of DnaB comprise two trypsin-resistant domains connected by a 45-amino-acid linker. To investigate the role of the linker in the structure and function of DnaB, we have purified and characterized three DnaB mutant proteins having single amino acid substitutions in the linker. We find that the mutant proteins retain the two-domain structure and assemble into hexamers that may be less stable than hexamers formed by wild-type DnaB. These mutant hexamers have hydrodynamic properties slightly different from those of the wild type, suggestive of a more open structure. The mutant proteins had reduced or absent ability to stimulate primase and also exhibited slight alterations in ATPase activity compared with the wild type. We conclude that the linker region promotes primase-DnaB interaction, but this effect may be indirect. We propose a model involving repositioning of N-terminal domains to explain the properties of the mutant proteins.

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“…The data were analyzed globally by the program NONLIN (nonlinear least squares analysis of sedimentation equilibrium data) of Johnson et al (18). Using the program SEQSEE (19), the partial specific volumes of LSAAN and LVAAN were calculated to be 0.71 and 0.73 mg/mL, respectively (20). The density of the solution was calculated to be 1.004 g/mL.…”

Section: Methodsmentioning

confidence: 99%

A Diminished Role for Hydrogen Bonds in Antifreeze Protein Binding to Ice

et al. 1997

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The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP 1 ) in winter flounder is a 37-amino-acid-long, alanine-rich, R-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {202 h1} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice.Type I AFP 1 is the smallest and arguably the simplest of the four macromolecular antifreeze types characterized to date (1). It is in effect a single, long R-helix and therefore lacks tertiary structure (2). The most abundant isoform of this AFP (HPLC-6) from winter flounder (Pleuronectes americanus) is 37 amino acids long, contains three complete 11-amino-acid repeats of Thr-X 2 -Asx-X 7 , where X is generally alanine, and ends with the start of a fourth repeat. This helical periodicity that places the Thr and Asx residues on the same face of the helix, suggested a mechanism for adsorption of the AFP to ice in which these regularly spaced hydrophilic groups would hydrogen bond to oxygen atoms in the ice lattice (3). Adsorption leads to inhibition of ice crystal growth (4) because ice is forced to grow with a surface curvature between the bound AFP, which in turn results in a lowering of the nonequilibrium freezing point below the melting point (5, 6). The difference in these two temperatures is termed thermal hysteresis and is used as a measure of antifreeze activity.At very low concentrations, AFP bind to ice but do not stop its growth. Under these conditions bound AFP is frozen into the ice rather than excluded by the advancing ice front. The protein binding planes in these crystals have been made visable by sublimation (ice etching) and determined to be the {202 h1} pyramidal plane of hexagonal ice (I h ) for type I AFP (5). Moreover, because this antifreeze is a nonglobular, extended molecule it was possible to establish a direction 〈011 h2〉 of binding on the plane. An elegant proof of this resulted from the synthesis of an all D-type I AFP, which was shown by the ice etching method to bind to the same plane but in the mirror image direction (7). This information was used to suggest a hydrogen-bonding match between the i, i + 11 threonines spaced 16.5 Å apart along the helix and accessible ice lattice oxygens spaced 16.7 Å apart along the 〈011 h2〉 direction of the {202 h1} binding plane.On the ba...

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PROTEINS, AMINO ACIDS AND PEPTIDES as Ions and Dipolar Ions

Cited by 475 publications

References 0 publications

Volume changes of the molten globule transitions of horse heart ferricytochrome c: A thermodynamic cycle

Volume changes of the molten globule transitions of horse heart ferricytochrome c: A thermodynamic cycle

Defect in general priming conferred by linker region mutants of Escherichia coli dnaB

A Diminished Role for Hydrogen Bonds in Antifreeze Protein Binding to Ice

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