Characterization of chromodulin by X-ray absorption and electron paramagnetic resonance spectroscopies and magnetic susceptibility measurements.
The biologically active form of the essential trace element chromium is believed to be the oligopeptide chromodulin. Chromodulin binds four chromic ions before binding at or near the active site of activating insulin receptor and subsequently potentiating the tyrosine kinase activity of the receptor. Charge balance arguments and preliminary spectroscopic studies suggested that the chromic centers might be part of a multinuclear assembly. Using a combination of X-ray absorption and electron paramagnetic resonance spectroscopies and variable-temperature magnetic susceptibility measurements, we found that holochromodulin is shown to possess an antiferromagnetically coupled trinuclear assembly which probably weakly interacts with a fourth chromium center. The chromium centers possess octahedron coordination comprised of oxygen-based ligation, presumably derived primarily from oligopeptide-supplied carboxylate groups. X-ray absorption data cannot be reproduced with the presence of sulfur atom(s), indicating that the cysteine thiolate group does not coordinate to the chromium centers. Thus, chromodulin possesses a unique type of multinuclear assembly, distinct from those known in other bioinorganic systems.
Jacquamet
Lilian
L
Department of Applied Science, University of California, Davis 95616, USA.
Sun
Yanjie
Y
Hatfield
Jason
J
Gu
Weiwei
W
Cramer
Stephen P
SP
Crowder
Michael W
MW
Lorigan
Gary A
GA
Vincent
John B
JB
Latour
Jean-Marc
JM
D002352:Carrier Proteins / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008280:Magnetics; D013052:Spectrometry, X-Ray Emission / Q000379:methods
D002352:Carrier Proteins; C406742:chromodulin protein, mouse; D002857:Chromium