Abstract
The unique spectroscopic properties of blue‐copper centers, i.e. the strong charge‐transfer band at approximately 600 nm and the narrow hyperfine coupling in the EPR spectrum, are reviewed. The concept of rack‐induced bonding is summarized. The tertiary structure of the protein creates a preformed chelating site with very little flexibility, the geometry of which is in conflict with that preferred by Cu2+. The structure of the metal site in azurin is discussed. It is shown that the three strong ligands, one thiolate S and two imidazole N, are in a configuration intermediate between those preferred by Cu2+ and Cu+. It is emphasized that cysteine is an obligatory component of a blue site, whereas the weak interaction with a methionine S is not necessary. The minimum rack energy is estimated to be 70 kJ · mol−1. It is pointed out that the high reduction potentials of blue‐copper centers are a result of the protein‐forced ligand‐field‐destabilized site structure. It is suggested that the potentials are tuned by variations in π back bonding, and this is supported by a linear increase in ΔLF (ligand field) with decreasing electron‐transfer enthalpy. Site‐directed mutagenesis has shown that large hydrophobic residues in the site increase the potential, whereas negative groups or water decrease it. It is also shown that the fine‐tuning of the properties of the metal site by rack‐induced bonding can alter the electron‐transfer reorganization energy. Kinetic results with azurin mutants support a through‐bond tunneling mechanism for intramolecular electron transfer in proteins. Finally, it is pointed out that the concept of rack‐induced bonding is a universal principle of macromolecular structure/function relationships, which should be applied also to other systems.
References
46
Referenced
217
10.1002/ijch.198100003
10.1016/0022-2836(88)90129-5
10.1016/S0006-291X(77)80084-3
10.1021/ja00306a025
10.1016/S0022-2836(62)80074-6
10.1016/0006-3002(63)90624-3
10.1016/0301-0104(90)89011-E
10.1016/0014-5793(93)81410-2
10.1021/bi00355a035
10.1038/272319a0
10.1021/ja00056a042
10.1021/bi00097a025
10.1016/S0020-1693(00)92355-7
/ Inorg. Chim. Acta 198–200 / Electronic absorption spectra of M(II)(Met121X) azurins (M = Co, Ni, Cu; X = Leu, Gly, Asp, Glu). Charge‐transfer energies and reduction potentials by Bilio A. J. (1992){'key': 'e_1_2_3_15_1', 'first-page': '123', 'volume-title': 'The mechanism of enzyme action', 'author': 'Eyring H.', 'year': '1954'}
/ The mechanism of enzyme action by Eyring H. (1954)10.1111/j.1432-1033.1992.tb17434.x
10.1016/0005-2728(68)90175-8
10.1016/S0021-9258(17)43220-0
/ J. Biol Chem. / The crystal structure of poplar apoplastocyanin at 1.8‐Å resolution. The geometry of the copper‐binding site is created by the polypeptide by Garret T. P. J. (1984)10.1021/bi00081a014
{'key': 'e_1_2_3_20_1', 'first-page': '1', 'volume-title': 'Copper proteins', 'author': 'Gray H. B.', 'year': '1981'}
/ Copper proteins by Gray H. B. (1981)10.1080/02603598308078118
10.1016/0162-0134(91)84164-5
10.1093/protein/4.3.343
- Karlsson G.(1993)Protein engineering on azurin.Expression mutagenesis and characterisation of copper site mutants. Ph. D. thesis Chalmers University of Technology.
10.1107/S0021889891004399
{'key': 'e_1_2_3_26_1', 'first-page': '455', 'volume-title': 'The biochemistry of copper', 'author': 'Lontie R.', 'year': '1966'}
/ The biochemistry of copper by Lontie R. (1966)10.1021/j150512a005
10.1016/S0022-2836(60)80034-4
{'key': 'e_1_2_3_29_1', 'first-page': '207', 'volume-title': 'Oxidases and related redox systems', 'author': 'Malmström B. G.', 'year': '1965'}
/ Oxidases and related redox systems by Malmström B. G. (1965)10.1016/0304-4173(85)90014-X
10.1111/j.1432-1033.1990.tb15311.x
10.1016/0022-2836(92)90583-6
10.1021/ja00051a059
10.1038/355796a0
10.1021/bi00059a013
10.1016/0022-2836(91)90723-J
10.1016/0014-5793(92)80981-L
10.1021/ja00270a064
10.1146/annurev.bb.21.060192.002025
{'key': 'e_1_2_3_40_1', 'first-page': '8', 'volume-title': 'Metals and enzyme activity', 'author': 'Orgel L. E.', 'year': '1958'}
/ Metals and enzyme activity by Orgel L. E. (1958)10.1111/j.1432-1033.1993.tb17661.x
10.1021/ja00177a065
10.1021/ja00521a029
10.1126/science.8384374
{'key': 'e_1_2_3_45_1', 'first-page': '133', 'volume-title': 'Molecular basis of enzyme action and inhibition', 'author': 'Williams R. J. P.', 'year': '1963'}
/ Molecular basis of enzyme action and inhibition by Williams R. J. P. (1963)10.1126/science.256.5059.1007
10.1016/0959-440X(93)90083-W
Dates
Type | When |
---|---|
Created | 20 years, 5 months ago (March 4, 2005, 5:51 a.m.) |
Deposited | 1 year, 10 months ago (Oct. 1, 2023, 10:06 a.m.) |
Indexed | 3 weeks, 4 days ago (Aug. 6, 2025, 8:07 a.m.) |
Issued | 31 years ago (Aug. 1, 1994) |
Published | 31 years ago (Aug. 1, 1994) |
Published Online | 20 years, 5 months ago (March 3, 2005) |
Published Print | 31 years ago (Aug. 1, 1994) |
@article{MALMSTR_M_1994, title={Rack‐induced bonding in blue‐copper proteins}, volume={223}, ISSN={1432-1033}, url={http://dx.doi.org/10.1111/j.1432-1033.1994.tb19044.x}, DOI={10.1111/j.1432-1033.1994.tb19044.x}, number={3}, journal={European Journal of Biochemistry}, publisher={Wiley}, author={MALMSTRÖM, Bo G.}, year={1994}, month=aug, pages={711–718} }