scholarly journals Binding of ferredoxin to algal photosystem I involves a single binding site and is composed of two thermodynamically distinct events

2018 ◽  
Vol 1859 (4) ◽  
pp. 234-243 ◽  
Author(s):  
Pini Marco ◽  
Marina Kozuleva ◽  
Haviva Eilenberg ◽  
Yuval Mazor ◽  
Peter Gimeson ◽  
...  
Keyword(s):  
Binding Site ◽  
Photosystem I ◽  
Single Binding Site

scholarly journals Induction of the Cellular E2F-1 Promoter by the Adenovirus E4-6/7 Protein

2000 ◽  
Vol 74 (5) ◽  
pp. 2084-2093 ◽  
Author(s):  
Joel Schaley ◽  
Robert J. O'Connor ◽  
Laura J. Taylor ◽  
Dafna Bar-Sagi ◽  
Patrick Hearing
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Transient Expression ◽  
Binding Sites ◽  
Promoter Region ◽  
Fluorescent Protein ◽  
Protein Accumulation ◽  
Promoter Regions ◽  
Single Binding Site

ABSTRACT The adenovirus type 5 (Ad5) E4-6/7 protein interacts directly with different members of the E2F family and mediates the cooperative and stable binding of E2F to a unique pair of binding sites in the Ad5 E2a promoter region. This induction of E2F DNA binding activity strongly correlates with increased E2a transcription when analyzed using virus infection and transient expression assays. Here we show that while different adenovirus isolates express an E4-6/7 protein that is capable of induction of E2F dimerization and stable DNA binding to the Ad5 E2a promoter region, not all of these viruses carry the inverted E2F binding site targets in their E2a promoter regions. The Ad12 and Ad40 E2a promoter regions bind E2F via a single binding site. However, these promoters bind adenovirus-induced (dimerized) E2F very weakly. The Ad3 E2a promoter region binds E2F very poorly, even via a single binding site. A possible explanation of these results is that the Ad E4-6/7 protein evolved to induce cellular gene expression. Consistent with this notion, we show that infection with different adenovirus isolates induces the binding of E2F to an inverted configuration of binding sites present in the cellular E2F-1 promoter. Transient expression of the E4-6/7 protein alone in uninfected cells is sufficient to induce transactivation of the E2F-1 promoter linked to chloramphenicol acetyltransferase or green fluorescent protein reporter genes. Further, expression of the E4-6/7 protein in the context of adenovirus infection induces E2F-1 protein accumulation. Thus, the induction of E2F binding to the E2F-1 promoter by the E4-6/7 protein observed in vitro correlates with transactivation of E2F-1 promoter activity in vivo. These results suggest that adenovirus has evolved two distinct mechanisms to induce the expression of the E2F-1 gene. The E1A proteins displace repressors of E2F activity (the Rb family members) and thus relieve E2F-1 promoter repression; the E4-6/7 protein complements this function by stably recruiting active E2F to the E2F-1 promoter to transactivate expression.

Phosphate Binding to Isolated Chloroplast Coupling Factor (CF1)

1988 ◽  
Vol 43 (3-4) ◽  
pp. 213-218 ◽  
Author(s):  
Bernhard Huchzermeyer
Keyword(s):  
Atpase Activity ◽  
Binding Site ◽  
Inorganic Phosphate ◽  
Coupling Factor ◽  
Binding Domain ◽  
Atp Binding ◽  
Phosphate Binding ◽  
Chloroplast Coupling Factor ◽  
Single Binding Site ◽  
Site Binding

A single binding site for phosphate was found on isolated chloroplast coupling factor in the absence of nucleotides. In our experiments the phosphate binding site showed a Kd of 170 μᴍ. We did not observe any differences whether the ATPase activity of CF] had been activated or not. If the enzyme was incubated with [γ-32P]ATP the amount of 32P bound per CF1 depended on the pretreatment of the enzyme: In the presence of ADP no ATP or phosphate was bound to CF,. After activation of ATPase activity one mol of ATP per mol CF, was rapidly bound and hydrolyzed while there was a slowly occurring binding of another phosphate without concomitant nucleotide binding. We conclude that there are two different types of phosphate binding observed in our experiments: 1) Inorganic phosphate can be bound by one catalytic site per mol of CF1 2) The γ-phosphate of ATP is able to bind to an ATP binding domain of the enzyme if this domain can exchange substrates with the incubation medium. This ATP binding domain appears to differ from the site binding inorganic phosphate, because at least a portion of the coupling factor contains more than one labelled phosphate during our ATPase tests.

scholarly journals Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

1978 ◽  
Vol 173 (1) ◽  
pp. 277-290 ◽  
Author(s):  
D J Lowe ◽  
R R Eady ◽  
R N F Thorneley
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Klebsiella Pneumoniae ◽  
Binding Site ◽  
Dissociation Constants ◽  
Paramagnetic Resonance ◽  
Fe Protein ◽  
Low Concentrations ◽  
Direct Binding ◽  
Electron Paramagnetic ◽  
Single Binding Site

Klebsiella pneumoniae nitrogenase exhibited four new electron-paramagnetic-resonance signals during turnover at 10 degrees C, pH7.4, which were assigned to intermediates present in low concentrations in the steady state. 57Fe-substituted Mo–Fe protein showed that they arose from Fe–S clusters in the Mo–Fe protein of nitrogenase. The new signals are designated: Ic, g values at 4.67, 3.37 and approx. 2.0; VI, g values at 2.125, 2.000 and 2.000; VII, g values at 5.7 and 5.4; VIII, g values at 2.092, 1.974 and 1.933. The sharp axial signal VI arises from a Fe4S4 cluster at the −1 oxidation level. This signal was only detected in the presence of ethylene and provides the first evidence of an enzyme–product complex for nitrogenase. [13C]Acetylene and [13C]ethylene provided no evidence for direct binding of this substrate and product to the Fe–S clusters giving rise to these signals. The dependence of signal intensities on acetylene concentration indicated two types of binding site, with apparent dissociation constants K less than 16 micron and K approximately 13mM. A single binding site for ethylene (K=1.5mM) was detected. A scheme is proposed for the mechanism of reduction of acetylene to ethylene and inhibition of this reaction by CO.

scholarly journals Two Compound Replication Origins in Saccharomyces cerevisiae Contain Redundant Origin Recognition Complex Binding Sites

2001 ◽  
Vol 21 (8) ◽  
pp. 2790-2801 ◽  
Author(s):  
James F. Theis ◽  
Carol S. Newlon
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Binding Site ◽  
Binding Sites ◽  
Origin Recognition Complex ◽  
Replication Origins ◽  
Discrete Site ◽  
Origin Function ◽  
Single Binding Site ◽  
Origin Recognition

ABSTRACT While many of the proteins involved in the initiation of DNA replication are conserved between yeasts and metazoans, the structure of the replication origins themselves has appeared to be different. As typified by ARS1, replication origins inSaccharomyces cerevisiae are <150 bp long and have a simple modular structure, consisting of a single binding site for the origin recognition complex, the replication initiator protein, and one or more accessory sequences. DNA replication initiates from a discrete site. While the important sequences are currently less well defined, metazoan origins appear to be different. These origins are large and appear to be composed of multiple, redundant elements, and replication initiates throughout zones as large as 55 kb. In this report, we characterize two S. cerevisiae replication origins, ARS101 and ARS310, which differ from the paradigm. These origins contain multiple, redundant binding sites for the origin recognition complex. Each binding site must be altered to abolish origin function, while the alteration of a single binding site is sufficient to inactivate ARS1. This redundant structure may be similar to that seen in metazoan origins.

scholarly journals Divalent Cation Interactions with Light-Dependent K Channels

1999 ◽  
Vol 114 (5) ◽  
pp. 653-672 ◽  
Author(s):  
Enrico Nasi ◽  
Maria del Pilar Gomez
Keyword(s):  
Binding Site ◽  
Single Channel ◽  
Divalent Cations ◽  
Light Response ◽  
Relaxation Methods ◽  
Physiological Conditions ◽  
Voltage Dependent ◽  
Single Channel Currents ◽  
Channel Currents ◽  
Single Binding Site

The light-dependent K conductance of hyperpolarizing Pecten photoreceptors exhibits a pronounced outward rectification that is eliminated by removal of extracellular divalent cations. The voltage-dependent block by Ca2+ and Mg2+ that underlies such nonlinearity was investigated. Both divalents reduce the photocurrent amplitude, the potency being significantly higher for Ca2+ than Mg2+ (K1/2 ≈ 16 and 61 mM, respectively, at Vm = −30 mV). Neither cation is measurably permeant. Manipulating the concentration of permeant K ions affects the blockade, suggesting that the mechanism entails occlusion of the permeation pathway. The voltage dependency of Ca2+ block is consistent with a single binding site located at an electrical distance of δ ≈ 0.6 from the outside. Resolution of light-dependent single-channel currents under physiological conditions indicates that blockade must be slow, which prompted the use of perturbation/relaxation methods to analyze its kinetics. Voltage steps during illumination produce a distinct relaxation in the photocurrent (τ = 5–20 ms) that disappears on removal of Ca2+ and Mg2+ and thus reflects enhancement or relief of blockade, depending on the polarity of the stimulus. The equilibration kinetics are significantly faster with Ca2+ than with Mg2+, suggesting that the process is dominated by the “on” rate, perhaps because of a step requiring dehydration of the blocking ion to access the binding site. Complementary strategies were adopted to investigate the interaction between blockade and channel gating: the photocurrent decay accelerates with hyperpolarization, but the effect requires extracellular divalents. Moreover, conditioning voltage steps terminated immediately before light stimulation failed to affect the photocurrent. These observations suggest that equilibration of block at different voltages requires an open pore. Inducing channels to close during a conditioning hyperpolarization resulted in a slight delay in the rising phase of a subsequent light response; this effect can be interpreted as closure of the channel with a divalent ion trapped inside.

A Comparison of Five Curve-Fitting Procedures in Radioimmunoassay

1986 ◽  
Vol 23 (6) ◽  
pp. 694-698 ◽  
Author(s):  
Jennifer A Nisbet ◽  
J A Owen ◽  
Gail E Ward
Keyword(s):  
Binding Site ◽  
Curve Fitting ◽  
The Other ◽  
Practical Advantage ◽  
Analytical Precision ◽  
Fitting Procedures ◽  
Best Fit ◽  
Single Binding Site ◽  
Better Than

Data obtained from routine analytical radioimmunoassays were processed using five curve-fitting procedures, viz. ‘Amersham’, single binding site, four parameter logistic, a linear logit-log and a polynomial logit-log. The polynomial logit-log procedure gave the best fit, but this was probably due to the inherent flexibility of this curve-fitting process since the analytical precision achieved with it was no better than what was obtained with most of the other procedures. A limited study failed to show that statistical weighting of data before curve fitting had any practical advantage.

Incorporation of 2,3-Disubstituted-1,4-Naphthoquinones into the A1 Binding Site of Photosystem I Studied by EPR and ENDOR Spectroscopy

2009 ◽  
Vol 37 (1-4) ◽  
pp. 65-83 ◽  
Author(s):  
Art van der Est ◽  
Yulia Pushkar ◽  
Irina Karyagina ◽  
Branden Fonovic ◽  
Travis Dudding ◽  
...  
Keyword(s):  
Binding Site ◽  
Photosystem I ◽  
Endor Spectroscopy

The Quinone Acceptor A1in Photosystem I:  Binding Site, and Comparison to QAin Purple Bacteria Reaction Centers

1998 ◽  
Vol 102 (42) ◽  
pp. 8278-8287 ◽  
Author(s):  
Andreas Kamlowski ◽  
Brigitte Altenberg-Greulich ◽  
Arthur van der Est ◽  
Stephan G. Zech ◽  
Robert Bittl ◽  
...  
Keyword(s):  
Binding Site ◽  
Photosystem I ◽  
Purple Bacteria ◽  
Reaction Centers ◽  
Quinone Acceptor

scholarly journals Scaffolding carbon nanotubes into single-molecule circuitry

2008 ◽  
Vol 23 (5) ◽  
pp. 1197-1201 ◽  
Author(s):  
Brett R. Goldsmith ◽  
John G. Coroneus ◽  
Jorge A. Lamboy ◽  
Gregory A. Weiss ◽  
Philip G. Collins
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Binding Site ◽  
Real Time ◽  
Single Molecule ◽  
Chemical Processes ◽  
Target Species ◽  
Single Walled Carbon Nanotube ◽  
Underlying Mechanisms ◽  
Single Binding Site

While nanowires and nanotubes have been shown to be electrically sensitive to various chemicals, not enough is known about the underlying mechanisms to control or tailor this sensitivity. By limiting the chemically sensitive region of a nanostructure to a single binding site, single molecule precision can be obtained to study the chemoresistive response. We have developed techniques using single-walled- carbon-nanotube (SWCNT) circuits that enable single-site experimentation and illuminate the dynamics of chemical interactions. Discrete changes in the circuit conductance reveal chemical processes happening in real-time and allow SWCNT sidewalls to be deterministically broken, reformed, and conjugated to target species.

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