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You might also find Phototransformation of green fluorescent protein with UV and visible light leads to decarboxylation of glutamate 222, van Thor JJ, Gensch T, Hellingwerf KJ, Johnson LN, Nature Structural Biology, 2002, 9, 37-41 relevant reading. Abstract below but a really interesting paper from the point of view of X-ray radiation damage.... Wild type green fluorescent protein (GFP) from Aequorea victoria absorbs predominantly at 398 nm. Illumination with UV (254 nm) or visible (390 nm) light transforms this state (GFP(398)) into one absorbing at 483 nm (GFP(483)). Here we show that this photoconversion of GFP is a one-photon process that is paralleled by decarboxylation of Glu 222. We propose a mechanism in which decarboxylation is due to electron transfer between the gamma-carboxylate of Glu 222 and the p-hydroxybenzylidene-imidazolidinone chromophore of GFP, followed by reverse transfer of an electron and a proton to the remaining carbon side chain atom of Glu 222. Oxidative decarboxylation of a gamma-carboxylate represents a new type of posttranslational modification that may also occur in enzymes with high-potential reaction intermediates. Cheers, Eddie. Edward Snell Ph.D. Assistant Prof. Department of Structural Biology, SUNY Buffalo, Hauptman-Woodward Medical Research Institute 700 Ellicott Street, Buffalo, NY 14203-1102 Phone: (716) 898 8631 Fax: (716) 898 8660 Email: [EMAIL PROTECTED] Telepathy: 42.2 GHz Heisenberg was probably here! -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David J. Schuller Sent: Tuesday, May 30, 2006 9:19 AM To: Artem Evdokimov Cc: [EMAIL PROTECTED] Subject: Re: [ccp4bb]: GFP losing coloration in X-ray beam? *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** This article is about a similar phenomenon, but not in GFPs. Nonetheless it is so impressive you should have a look at it: --- Berglund, GL, Carlsson, GH, Smith, AT, Szoke, H, Henriksen, A, Hajdu, J, The catalytic pathway of horseradish peroxidase at high resolution NATURE 417 (6887): 463-468 MAY 23 2002 Abstract: A molecular description of oxygen and peroxide activation in biological systems is difficult, because electrons liberated during X-ray data collection reduce the active centres of redox enzymes catalysing these reactions(1-5). Here we describe an effective strategy to obtain crystal structures for high-valency redox intermediates and present a three-dimensional movie of the X-ray-driven catalytic reduction of a bound dioxygen species in horseradish peroxidase (HRP). We also describe separate experiments in which high-resolution structures could be obtained for all five oxidation states of HRP, showing such structures with preserved redox states for the first time. --- On Mon, 2006-05-29 at 15:52 -0400, Artem Evdokimov wrote: > ...I have noticed a peculiar phenomenon: during the very first X-ray > exposure, the normally intensely greenish-yellow color of the crystals > completely disappeared within the area that was hit by the beam. That > was happening in real time, while the crystal was still frozen. There > was no significant deterioration of diffraction quality, and the > structures were successfully solved using these data. We noted no > anomalies in the chromophore as such - it looks like a typical GFP > heterocycle, although the resolution isn't sufficient to refine w/o > restraints and thus verify the exact bond types etc. > Here's the question - does anyone know of a published report of this > phenomenon, as related to other GFPs, or other colored/fluorescent > beta-barrel proteins? We couldn't find any, but that doesn't mean that > there wasn't a mention in one of the dozens of GFP structural papers. -- ======================================================================= I think we're all bugs and mice, and are only different expressions of an all-inclusive cheese. - Charles Fort ======================================================================= David J. Schuller modern man in a post-modern world MacCHESS, Cornell University [EMAIL PROTECTED]
