Question

The green fluorescent protein and 4-methylideneimidazole-5-one (MIO) containing enzymes, have a cofactors made from the cyclization of three amino acids. Draw the structure of MIO and the green fluorescent protein chromophore, then circle atoms derived from each amino acid.

Answer 1

Green fluorescent protein (GFP) is a fluorescent protein that was originally isolated from the luminous organ of the jellyfish Aequorea victoria by Dr. Osamu Shimomura. The main reason why GFP is so revolutionary is its ability to be easily introduced into cells by transfection, which is dependent on a key feature of GFP, that is, its ability to generate the intrinsic chromophore without cofactors or enzymatic components.

The prosthetic group 4-methylideneimidazole-5-one (MIO) is the catalytic component of the ammonia lyase class of enzymes. This family is responsible for the processing of amino acids in a variety of metabolic pathways through the elimination of ammonia to form unsaturated products.

When the structure of MIO was determined, it was recognized that the MIO prosthetic group was similar in structure to the GFP chromophore. Each was the result of a post-translational modification of the protein backbone that resulted in a tri-peptide cyclization event; with MIO formed from and Ala-Ser-Gly motif and GFP formed from Ser-Tyr-Gly.

R = Is a continuation of the peptide backbone.