Linked Life Data

12817956

Source:http://linkedlifedata.com/resource/pubmed/id/12817956

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
2003-6-23
pubmed:abstractText
A variety of spectroscopic techniques, combined with density functional calculations, are used to describe the electronic structure of the Leu513His variant of the type 1 Cu site in Myceliophthora thermophila laccase. This mutation changes the type 1 Cu from a blue to a green site. Electron paramagnetic resonance (EPR), optical absorption, circular dichroism, and magnetic circular dichroism (MCD) spectroscopies reveal that, relative to the trigonal planar blue type 1 Cu site in wild-type fungal laccase, the covalency and the ligand field strength at the Leu513His green type 1 Cu center decrease. Additionally, there is a significant reorientation of the d(x)()()2(-)(y)()()2( )singly occupied MO, such that the overlap with the Cys sulfur valence orbital changes from pi to sigma. A density functional study in which internal coordinates are systematically altered reveals that these changes are due to the increased strength of the axial ligand (none to His), leading to a tetragonal distortion and elongation of the equatorial Cu-ligand bonds. These calculations provide insight into the experimental differences in the EPR parameters, charge-transfer absorption spectrum, and ligand-field MCD spectrum between the axial-His variant and blue Cu centers (plastocyanin and the type 1 site in fungal laccase). There are also significant differences between the green site in the Leu513His variant and other naturally occurring, green type 1 Cu sites such as in nitrite reductase, which have short axial Cu-S(Met) bonds. The large difference in EPR parameters between these green type 1 sites derives from a change in ligand field excitation energies observed by MCD, which reflects a decrease in ligand field strength. This is associated with different steric interactions of a His vs an axial Met ligand in a tetragonally distorted type 1 site. Changes in the electronic structure of the Cu site correlate with the difference in reactivity of the green His variant relative to blue wild-type fungal laccase.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0020-1669
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
42
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4006-17
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Spectroscopic characterization of the Leu513His variant of fungal laccase: effect of increased axial ligand interaction on the geometric and electronic structure of the type 1 Cu site.
pubmed:affiliation
Department of Chemistry, Stanford University, Stanford, California 94305 and Novozymes Biotech, Davis, California 95616, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't