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The influence of axial ligands on the reduction potential of blue copper proteins

Olsson, Mats H M LU and Ryde, Ulf LU (1999) In Journal of Biological Inorganic Chemistry 4(5). p.654-663
Abstract

The reduction potentials of blue copper sites vary between 180 and about 1000 mV. It has been suggested that the reason for this variation is that the proteins constrain the distance between the copper ion and its axial ligands to different values. We have tested this suggestion by performing density functional B3LYP calculations on realistic models of the blue copper proteins, including solvent effects by the polarizable continuum method. Constraining the Cu-S(Met) bond length to values between 245 and 310 pm (the range encountered in crystal structures) change the reduction potential by less than 70 mV. Similarly, we have studied five typical blue copper proteins spanning the whole range of reduction potentials: stellacyanin,... (More)

The reduction potentials of blue copper sites vary between 180 and about 1000 mV. It has been suggested that the reason for this variation is that the proteins constrain the distance between the copper ion and its axial ligands to different values. We have tested this suggestion by performing density functional B3LYP calculations on realistic models of the blue copper proteins, including solvent effects by the polarizable continuum method. Constraining the Cu-S(Met) bond length to values between 245 and 310 pm (the range encountered in crystal structures) change the reduction potential by less than 70 mV. Similarly, we have studied five typical blue copper proteins spanning the whole range of reduction potentials: stellacyanin, plastocyanin, azurin, rusticyanin, and ceruloplasmin. These studies included the methionine (or glutamine) ligand as well as the back-bone carbonyl oxygen group that is a ligand in azurin and is found at larger distances in the other proteins. The active-site models of these proteins show a variation in the reduction potential of about 140 mV, i.e., only a minor part of the range observed experimentally (800 mV). Consequently, we can conclude that the axial ligands have a small influence on the reduction potentials of the blue copper proteins. Instead, the large variation in the reduction potentials seems to arise mainly from variations in the solvent accessibility of the copper site and in the orientation of protein dipoles around the copper site.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
Blue copper protein, Entatic state theory, Induced rack theory, Quantum chemical calculations, Reduction potential
in
Journal of Biological Inorganic Chemistry
volume
4
issue
5
pages
10 pages
publisher
Springer
external identifiers
  • scopus:0032758351
ISSN
0949-8257
DOI
10.1007/s007750050389
language
English
LU publication?
yes
id
69755985-c240-4cc4-844f-9f70264886d7
date added to LUP
2017-02-04 11:42:02
date last changed
2017-05-10 16:52:24
@article{69755985-c240-4cc4-844f-9f70264886d7,
  abstract     = {<p>The reduction potentials of blue copper sites vary between 180 and about 1000 mV. It has been suggested that the reason for this variation is that the proteins constrain the distance between the copper ion and its axial ligands to different values. We have tested this suggestion by performing density functional B3LYP calculations on realistic models of the blue copper proteins, including solvent effects by the polarizable continuum method. Constraining the Cu-S(Met) bond length to values between 245 and 310 pm (the range encountered in crystal structures) change the reduction potential by less than 70 mV. Similarly, we have studied five typical blue copper proteins spanning the whole range of reduction potentials: stellacyanin, plastocyanin, azurin, rusticyanin, and ceruloplasmin. These studies included the methionine (or glutamine) ligand as well as the back-bone carbonyl oxygen group that is a ligand in azurin and is found at larger distances in the other proteins. The active-site models of these proteins show a variation in the reduction potential of about 140 mV, i.e., only a minor part of the range observed experimentally (800 mV). Consequently, we can conclude that the axial ligands have a small influence on the reduction potentials of the blue copper proteins. Instead, the large variation in the reduction potentials seems to arise mainly from variations in the solvent accessibility of the copper site and in the orientation of protein dipoles around the copper site.</p>},
  author       = {Olsson, Mats H M and Ryde, Ulf},
  issn         = {0949-8257},
  keyword      = {Blue copper protein,Entatic state theory,Induced rack theory,Quantum chemical calculations,Reduction potential},
  language     = {eng},
  number       = {5},
  pages        = {654--663},
  publisher    = {Springer},
  series       = {Journal of Biological Inorganic Chemistry},
  title        = {The influence of axial ligands on the reduction potential of blue copper proteins},
  url          = {http://dx.doi.org/10.1007/s007750050389},
  volume       = {4},
  year         = {1999},
}