Manganese electron paramagnetic resonance studies of sheep kidney (sodium(1+) + potassium(1+) ion) transport adenosine triphosphatase. Interactions of substrates and activators at a single manganese(2+) ion-binding site

Biochemistry ◽  
1979 ◽  
Vol 18 (11) ◽  
pp. 2315-2323 ◽  
Author(s):  
Sally E. O'Connor ◽  
Charles M. Grisham
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ion Transport ◽  
Binding Site ◽  
Adenosine Triphosphatase ◽  
Ion Binding ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

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 Synthesis and electron paramagnetic resonance studies of chiral spin-labeled crown ethers

1984 ◽  
Vol 62 (3) ◽  
pp. 489-497 ◽  
Author(s):  
H. Dugas ◽  
P. Keroack ◽  
M. Ptak
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crown Ether ◽  
Crown Ethers ◽  
Spin Interaction ◽  
Ion Binding ◽  
Paramagnetic Resonance ◽  
Dynamical Fluctuation ◽  
Electron Paramagnetic

The synthesis of syn and anti chiral dinitroxide [18]-crown-6 ethers and of a tetranitroxide crown ether is described. The existence of a spin–spin interaction for the syn isomer makes this spin-labeled crown ether probe particularly useful to follow by epr the effects of K+ ion binding, pH, solvent, and temperature. These observations are discussed in terms of a global dynamical fluctuation of the substituted crown ether.

Conformational changes at the nucleotide pocket of motor proteins monitored by electron paramagnetic resonance spectroscopy

2011 ◽  
Vol 83 (9) ◽  
pp. 1675-1684 ◽  
Author(s):  
Nariman Naber ◽  
Roger Cooke ◽  
Edward Pate
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Binding Site ◽  
Conformational Changes ◽  
Motor Proteins ◽  
Nucleotide Binding ◽  
Nucleotide Binding Site ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Nucleotide Site ◽  
Electron Paramagnetic

A fundamental goal in the field of motor proteins is to identify the conformational changes associated with the hydrolysis of the physiological substrate, ATP, and to define how these conformational changes are modulated by binding to the polymer track and translated into biologically useful movement. We have used electron paramagnetic resonance (EPR) spectroscopy to monitor conformational changes at the nucleotide-binding site of myosin- and kinesin-family motors. A novel set of nucleotide-analog EPR spin probes were synthesized and used to localize a spin moiety at the nucleotide site. This allows a reporter group to be placed with high specificity at the ATP binding site. Our results indicate that the nucleotide-binding site of myosin motors opens when the motor binds to its polymer roadway, actin, while that of kinesin closes on binding to microtubules (MTs). However, the transition is not all-or-none. There is instead an equilibrium between open and closed conformations. The different conformational changes in the two motor families can be correlated with differences in their biochemical cycles. Thus, we can now define the relationship between nucleotide-site structure, biochemistry and polymer binding for the two motors.

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