title: A conserved interaction with the chromophore of fluorescent proteins.
abstract: The chromophore of fluorescent proteins, including the green fluorescent protein (GFP), contains a highly conjugated imidazolidinone ring. In many fluorescent proteins, the carbonyl group of the imidazolidinone ring engages in a hydrogen bond with the side chain of an arginine residue. Prior studies have indicated that such an electrophilic carbonyl group in a protein often accepts electron density from a main-chain oxygen. A survey of high-resolution structures of fluorescent proteins indicates that electron lone pairs of a main-chain oxygen-Thr62 in GFP-donate electron density into an antibonding orbital of the imidazolidinone carbonyl group. This n→π* electron delocalization prevents structural distortion during chromophore excitation that could otherwise lead to fluorescence quenching. In addition, this interaction is present in on-pathway intermediates leading to the chromophore, and thus could direct its biogenesis. Accordingly, this n→π* interaction merits inclusion in computational and photophysical analyses of the chromophore, and in speculations about the molecular evolution of fluorescent proteins.
authors: Graduate Program in Biophysics, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors: Amit
authors: A
authors: Choudhary
authors: Kimberli J
authors: KJ
authors: Kamer
authors: Ronald T
authors: RT
authors: Raines
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain / Q000235:genetics; D002863:Chromogenic Compounds / Q000737:chemistry / Q000378:metabolism*; D017124:Conserved Sequence / Q000502:physiology; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D048289:Imidazolidines / Q000737:chemistry / Q000378:metabolism; D008164:Luminescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000235:genetics
chemical_list: D002863:Chromogenic Compounds; D048289:Imidazolidines; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins