Conformational changes in plastocyanin

Draheim, James E.; Anderson, George P.; Pan, Rong; Rellick, Lorraine M.; Duane, J.W.; Gross, Elizabeth

doi:10.1016/0003-9861(85)90259-0

Cited by 20 publications

(10 citation statements)

References 20 publications

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“…The extinction of PC increases significantly upon reduction throughout the near-UV below 310 nm. This phenomenon was the subject ' 4 ***y5,2ffiisof a previous study (Draheim et al, 1985). Some minor absorption bands (-320-330 nm) were either lost or diminished upon forming apo PC.…”

Section: Fumentioning

confidence: 79%

“…Previously, this laboratory has shown that in solution PC undergoes conformational changes both upon changing redox state and upon EDA chemical modification (Draheim et al, 1985) as determined by near-UV absorption, circular dichroism (CD) and fluorescence measurements. These conformational changes are probably quite small in magnitude (subtle) but Gross et al (1985) have provided evidence that they are global in scale.…”

Section: Introductionmentioning

confidence: 99%

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Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Draheim¹,

Anderson²,

Duane³

et al. 1986

Biophysical Journal

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The near-ultraviolet absorption and circular dichroic spectra of plastocyanin are dependent upon the redox state, solution pH, and ammonium sulfate concentration. This dependency was observed in plastocyanin isolated from spinach, poplar, and lettuce. Removal of the copper atom also perturbed the near-ultraviolet spectra. Upon reduction there are increases in both extinction and ellipticity at 252 nm. Further increases at 252 nm were observed upon formation of apo plastocyanin eliminating charge transfer transitions as the cause. The spectral changes in the near-ultraviolet imply a flexible tertiary conformation for plastocyanin. There are at least two charge transfer transitions at approximately 295-340 nm. One of these transitions is sensitive to low pH's and is attributed to the His 87 copper ligand. The redox state dependent changes observed in the near-ultraviolet spectra of plastocyanin are attenuated either by decreasing the pH to 5 or by increasing the ammonium sulfate concentration to 2.7 M. This attenuation cannot be easily explained by simple charge screening. Hydrophobic interactions probably play an important role in this phenomenon. The pH and redox state dependent conformational changes may play an important role in regulating electron transport.

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Section: Fumentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Draheim¹,

Anderson²,

Duane³

et al. 1986

Biophysical Journal

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“…Andrew et al, 1994). Very small changes in tertiary structure have also been proposed to explain differences between the near-ultraviolet spectra of Pc(Cu1) and Pc(CuI1) (Draheim et al, 1985).…”

Section: Discussionmentioning

confidence: 99%

Analysis of the ¹H‐NMR Chemical Shifts of Cu(I)‐, Cu(II)‐ and Cd‐Substituted Pea Plastocyanin

Ubbink

Lian

Modi

et al. 1996

European Journal of Biochemistry

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To compare cadmium-substituted plastocyanin with copper plastocyanin, the 'H-NMR spectra of CuI-, Curl-and Cd-plastocyanin from pea have been analyzed. Full assignments of the spectra of CuIand Cd-plastocyanin indicate chemical shift differences up to 1 ppm. The affected protons are located in the four loops that surround the Cu site. The largest differences were found for protons in the hydrogen bond network which stabilizes this part of the protein. This suggests that the chemical shift differences are caused by very small but extensive structural changes in the network upon replacement of CuI by Cd.For CuII-plastocyanin the resonances of 72% of the protons observed in the Cul form have been identified. Protons within =0.9 nm of the CuII were not observed due to fast paramagnetic relaxation. The protons between 0.9 -1.7 nm from the CuII showed chemical shift differences up to 0.4 ppm compared to both Cur-and Cd-plastocyanin. These differences can be predicted assuming that they represent pseudocontact shifts. When corrected for the pseudocontact shift contribution, the CuII-plastocyanin chemical shifts were nearly all identical within error to those of the Cd form, but not of the CuI-plastocyanin, indicating that the CuII-plastocyanin structure, in as far as it can be observed, resembles Cd-rather than CuI-plastocyanin. In a single stretch of residues (64-69) chemical shift differences remained between all three forms after correction.The fact that pseudocontact shifts were observed for protons which were not broadened may be attributable to the weaker distance dependence of the pseudocontact shift effect compared to paramagnetic relaxation. This results in two shells around the Cu atom, an inner paramagnetic shell (0-0.9 nm), in which protons are not observed due to broadening, and an outer paramagnetic shell (0.9-1.7 nm), in which protons can be observed and show pseudocontact shifts.Keywords: plastocyanin ; chemical shift; paramagnetic ; azurin ; cadmium.It is concluded that Cd-plastocyanin is a suitable redox-inactive substitute for Cu-plastocyanin.Plastocyanin is a small (10.4 kDa) type-I copper protein that functions as a soluble electron carrier in the lumen of thylakoid vesicles in chloroplasts. It shuttles electrons from the cytochrome lf complex to photosystem I (PSI), both of which are located in the thylakoid membrane. There is much interest in the question of how plastocyanin interacts with its redox partners. The protein has two obvious potential sites for electron transfer. First, the so-called hydrophobic patch at the top or north side of the protein in the conventional representation (Fig. 1) which provides the shortest route for the electron to reach the copper atom, via the ligand H87. Secondly, the acidic patch (at the east side) which requires a longer pathway for electron transfer (via ligand C84 and surface residue Y83) but contains two clusters of negative charges, which are potentially favourable for electrostatic interaction between plastocyanin and the redox partners.A variety of tec...

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“…PC was isolated from spinach and poplar (Populus deltoides) according to the methods of Davis and San Pietro (21) and Graziani et al (22) respectively. Further purification was carried out by FPLC using a Mono-Q anion exchange column + a linear NaCl gradient.…”

Section: Methodsmentioning

confidence: 99%

“…The region above 285 nm may be due to charge transfer bands possibly associated with histidine residues (28). Changing the oxidation state of PC primarily affects the phenylalanine and charge tranfer regions (22,29). Lowering the pH also affects these two regions.…”

Section: Methodsmentioning

confidence: 99%

pH dependent conformational changes and electrostatic effects in plastocyanin

et al. 1986

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Reduction of plastocyanin (PC) caused a change in the electric field at the surface of the molecule which resulted in a 0.3 pH unit increase in the pKa of a nitrated derivative of Tyr 83. This change in electrical potential could alter the affinity for cytochrome f which is known to bind at this site. Conversely, properties of the copper center, including the pH dependence of the reduction potential, are regulated by the charge on the surface of the molecule. Both the reduction potential and conformation (as measured by near-UV circular dichroic spectra) were pH dependent. Thus the conformation and electrostatic behavior of PC are dependent on oxidiation state, pH and surface charge, raising the possibility that its redox activity is controlled by the pH gradient.

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Conformational changes in plastocyanin

Cited by 20 publications

References 20 publications

Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Analysis of the ¹H‐NMR Chemical Shifts of Cu(I)‐, Cu(II)‐ and Cd‐Substituted Pea Plastocyanin

pH dependent conformational changes and electrostatic effects in plastocyanin

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Conformational changes in plastocyanin

Cited by 20 publications

References 20 publications

Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Plastocyanin conformation. An analysis of its near ultraviolet absorption and circular dichroic spectra

Analysis of the 1H‐NMR Chemical Shifts of Cu(I)‐, Cu(II)‐ and Cd‐Substituted Pea Plastocyanin

pH dependent conformational changes and electrostatic effects in plastocyanin

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Analysis of the ¹H‐NMR Chemical Shifts of Cu(I)‐, Cu(II)‐ and Cd‐Substituted Pea Plastocyanin