Reactions of electron-transfer proteins at electrodes

Fa, Armstrong; Allen, Harry C.; Hill, O.; Nj, Walton

doi:10.1017/s0033583500000366

Cited by 148 publications

(52 citation statements)

References 114 publications

(94 reference statements)

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“…The term ⌬G* comprises contributions from aqueous solvent hydration shell reorganization energies. k el varies exponentially with r(Å), the distance separating the donor and acceptor molecules; for r ϭ 12 Å, k el has been predicted to be 6 ϫ 10 Ϫ6 (43). From the FRET experiments reported above, the experimental value for the distance between the galactosyl moiety of GalCer and the lectin binding site of gp41 is Ͻ15 Å.…”

Section: Computation Of the Free Energy Of Activation Of The Electronmentioning

confidence: 98%

HIV-1 gp41 Envelope Residues 650–685 Exposed on Native Virus Act as a Lectin to Bind Epithelial Cell Galactosyl Ceramide

Alfsen

Bomsel

2002

Journal of Biological Chemistry

110

126

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The initial step in the interaction between human immunodeficiency virus (HIV-1) and epithelial cells is the binding of HIV-1 envelope glycoproteins to the epithelial cell galactosyl ceramide (GalCer). Here we show that HIV-1 envelope gp41 residues 650 -685 bind GalCer in a galactose-specific manner. The gp41 residues that display this lectin activity are highly conserved among HIV-1 isolates and constitute three regions: residues 650 -661, which encompass a charged helix; residues 662-667, referred to as the conserved epitope ELDKWA, the epitope recognized by antibodies that neutralize HIV-1 entry in epithelial and CD4؉ -mononucleated cells; and residues 668 -685, a hydrophobic Trp-rich sequence that stabilizes the structure of the galactose binding site. Similar to other galactose-specific lectins, the gp41 lectin site is active only as an oligomer. Finally the orientation of the galactose toward the gp41 lectin site appears to be controlled by the lipid microenvironment of the epithelial membrane. From the experimental data we construct a theoretical model of the interaction between gp41 and GalCer based on thermodynamic considerations. This model integrates the dynamics and the spatial organization of the viral envelope glycoproteins, GalCer organized in raft microdomains in the apical region of the epithelial cell membrane and the interfacial water. Characterization of the minimal sequence and structure of gp41 in direct interaction with GalCer may help unravel the still unknown immunogenic determinant able to elicit antibodies against ELDKWA and target of one of the rare neutralizing antibodies against gp41.

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Section: Computation Of the Free Energy Of Activation Of The Electronmentioning

confidence: 98%

HIV-1 gp41 Envelope Residues 650–685 Exposed on Native Virus Act as a Lectin to Bind Epithelial Cell Galactosyl Ceramide

Alfsen

Bomsel

2002

Journal of Biological Chemistry

110

126

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“…Cyclic voltammetry at a viologenmodified glassy carbon electrode showed a quasi-reversible response around Em = -367 mV. Van Dijk et al concluded this finding to reflect direct electrochemistry of the ferredoxin [32]; however, Armstrong et al have suggested surface mediation as an alternative interpretation [2].…”

Section: Direct Responses Of Other Redox Proteins At Bare Glassy Carbonmentioning

confidence: 99%

“…The methodological hows and whys appear to a considerable extent to have been established by now in studies employing small, electron-transferring proteins [2]. The first successful detection of electron transfer between a true enzyme and a solid electrode was recently reported [3].…”

mentioning

confidence: 99%

Direct electron transfer of redox proteins at the bare glassy carbon electrode

Hagen¹

1989

European Journal of Biochemistry

146

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A simple system is presented for the microscale, direct voltammetry of redox proteins, typically 25 pg, in the absence of mediators and/or modifiers. The sample consists of a droplet of anaerobic solution laid onto an oversized disc of nitric-acid-pretreated glassy carbon as the working electrode. Very reproducible, Nernstian responses are obtained with horse heart cytochrome c. The midpoint potential Em (pH 7.0) is dependent on the ionic strength, ranging from +293 mV in 1 mM potassium phosphate to +266 mV in 0.1 M phosphate. At fixed buffer and cytochrome concentrations the magnitude of the voltammetric response is found to be independent of pH over six pH units around neutrality. It is suggested that the response of the present system is not complicated by pH-dependent properties of the electrode surface around physiological pH and, therefore, that the use of this system is practical in biochemically oriented studies. Direct, quasi-reversible responses have also been obtained at pH 7.0 (5 mM phosphate) from DesuEfovibrio vulgaris. Hildenborough strain, tetraheme cytochrome c3 (PI = 10.0 at 4°C; 3 x Em = -0.32 mV, Em = -0.26 V), and cytochrome c S s 3 (PI = 9.3; Em = +60 mV), and from Megasphaera elsdenii rubredoxin (PI 'v 3; Em = f 4 2 mV) and 2[4Fe-4S] ferredoxin (PI 'v 3; Em = -353 mV). The latter protein adsorbs onto the glassy carbon surface, thus forming a system with possible applications in the electrochemical study of ferredoxin-linked enzymes.Direct, unmediated bioelectrochemistry at solid electrodes has been developed over the last decade from an academic possibility to a potentially powerful method for mechanistic studies on redox proteins [l]. The methodological hows and whys appear to a considerable extent to have been established by now in studies employing small, electron-transferring proteins [2]. The first successful detection of electron transfer between a true enzyme and a solid electrode was recently reported [3].Essentially, two different approaches have been tried to achieve direct, (quasi-)reversible electrode responses of redox proteins. The group of Hill and coworkers has been at the forefront of developing efficient and, possibly, specific promoters of bioelectrochemistry and trying to understand their mechanisms of action on the molecular level [I, 21. The notion, promoter, here means any substance that does not take part in the electron transfer in the electrochemical potential range of interest, but rather maneuvers itself in a specific manner between the redox protein and the electrode surface (i.e. the kinetic formation of a heterogeneous trimeric complex) such as to promote reversible electron transfer. Alternatively, these and other workers have taken the approach to do without promoters by developing special pretreatment procedures and experimental protocol for the use of bare electrodes with proteins, e.g. [ l , 2, 4-81, The point has been made that high purity of protein preparation is an essential factor in the reproducibility of responses on bare electrodes [9].The method...

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“…The strong interest in this small soluble haem protein is, on the one hand, related to its important physiological functions in the respiratory chain of aerobic organisms and in apoptotic pathways [1][2][3][4]. On the other hand, owing to its small size, its well-characterised structural and spectral properties as well as the availability of engineered protein variants, cytochrome c is frequently used as model protein for studying fundamental biophysical processes such as electron transfer [5][6][7][8][9] and protein folding [10][11][12][13][14][15][16][17]. Specifically, the elucidation of relationships between protein folds and dynamics and the electron transfer properties is of particular interest in view of its impact for understanding biological processes on a molecular level and for the design of novel tailor-made redox enzymes for potential biotechnological applications.…”

Section: Introductionmentioning

confidence: 99%

The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

et al. 2010

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We have studied the effect of urea-induced unfolding on the electron transfer process of yeast iso-1-cytochrome c and its mutant K72AK73AK79A adsorbed on electrodes coated by mixed 11-mercapto-1-undecanoic acid/ 11-mercapto-1-undecanol self-assembled monolayers. Electrochemical measurements, complemented by surface enhanced resonance Raman studies, indicate two distinct states of the adsorbed proteins that mainly differ with respect to the ligation pattern of the haem. The native state, in which the haem is axially coordinated by Met80 and His18, displays a reduction potential that slightly shifts to negative values with increasing urea concentration. At urea concentrations higher than 6 M, a second state prevails in which the Met80 ligand is replaced by an additional histidine residue. This structural change in the haem pocket is associated with an approximately 0.4 V shift of the reduction potential to negative values. These two states were found for both the wild-type protein and the mutant in which lysine residues 72, 73 and 79 had been substituted by alanines. The analysis of the reduction potentials, the reaction enthalpies and entropies as well as the rate constants indicates that these three lysine residues have an important effect on stabilising the protein structure in the adsorbed state and facilitating the electron transfer dynamics.

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Reactions of electron-transfer proteins at electrodes

Cited by 148 publications

References 114 publications

HIV-1 gp41 Envelope Residues 650–685 Exposed on Native Virus Act as a Lectin to Bind Epithelial Cell Galactosyl Ceramide

HIV-1 gp41 Envelope Residues 650–685 Exposed on Native Virus Act as a Lectin to Bind Epithelial Cell Galactosyl Ceramide

Direct electron transfer of redox proteins at the bare glassy carbon electrode

The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

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