if you don't see a molecular model:
http://www.biologie.uni-hamburg.de/
lehre/bza/light/gfp/gfpm.htm

To highlight described properties click the boxes

. Move the molecules anytime with the mouse - if the view is messed up, clicking the large boxes

will restore a convenient view.

Green Fluorescent Protein
from Aequorea victoria

The blue chemiluminescence of aequorin is transformed in the jellyfish Aequorea victoria by green fluorescent protein (GFP) into green light. The prominent structural feature of GFP is a pleated sheet of eleven strands that is wrapped to form a barrel. The strands are antiparallel

with the exception of the seam (with an odd number two strands have to be parallel)

. In the middle part of the sheet the strands are connected to form a greek key motif (also called a jellyroll), as seen in the scheme:

The barrel formed by the sheet is slightly oval in cross-section. Along the center of the barrel runs a stretch of amino acids which looks like a very distorted helix . Some of the residues are arranged in a helical pattern . The structure in between is something special : here you find the chromophore which is formed from amino acids Ser⁶⁵ , Tyr⁶⁶ and Gly⁶⁷ by an internal cyclization reaction according to this pathway:

The initiation of the cyclization reaction requires the amide N of Gly⁶⁷ to be in close enough contact to the carbonyl of Ser⁶⁵, which is the case only after proper folding of the whole protein. The oxidation step generates a large conjugated resonant pi-electron system capable of light absorption.
The chromophore is held in place by several amino acids

which form a tight hydrogen bond network

including some fixed water molecules (distances for possible hydrogen bonds given in Å).

Though the wall of the beta-barrel is only one aminoacid thick, it completely shields the chromophore from the surrounding solvent . The barrel got some lids, too, both on bottom and top , to make the whole structure watertight (don't worry about the light - electromagnetic radiation will easily pass the protein layer).

Restart this demonstration

Literature:
F Yang et al, The molecular structure of green fluorescent protein, Nature Biotechnology 14 (1996) 1246-1251
M Ormö et al, Crystal structure of the Aequoria victoria green fluorescent protein, Science 273 (1996) 1392-1395

3-03 - Rolf Bergmann

Green Fluorescent Protein from Aequorea victoria

Green Fluorescent Protein
from Aequorea victoria