title: Tryptophan-based fluorophores for studying protein conformational changes.
abstract: With the continuing interest in deciphering the interplay between protein function and conformational changes, small fluorescence probes will be especially useful for tracking changes in the crowded protein interior space. Presently, we describe the potential utility of six unnatural amino acid fluorescence donors structurally related to tryptophan and show how they can be efficiently incorporated into a protein as fluorescence probes. We also examine the various photophysical properties of the new Trp analogues, which are significantly redshifted in their fluorescence spectra relative to tryptophan. In general, the Trp analogues were well tolerated when inserted into Escherichia coli DHFR, and did not perturb enzyme activity, although substitution for Trp22 did result in a diminution in DHFR activity. Further, it was demonstrated that D and E at position 37 formed efficient FRET pairs with acridon-2-ylalanine (Acd) at position 17. The same was also true for a DHFR construct containing E at position 79 and Acd at position 17. Together, these findings demonstrate that these tryptophan analogues can be introduced into DHFR with minimal disruption of function, and that they can be employed for the selective study of targeted conformational changes in proteins, even in the presence of unmodified tryptophans.
authors.affiliation: Center for BioEnergetics, Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Poulami
authors.initials: P
authors.lastname: Talukder
authors.affiliation: Center for BioEnergetics, Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Shengxi
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: C Tony
authors.initials: CT
authors.lastname: Liu
authors.affiliation: Center for BioEnergetics, Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Edwin A
authors.initials: EA
authors.lastname: Baldwin
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA. Electronic address: sjb1@psu.edu.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Benkovic
authors.affiliation: Center for BioEnergetics, Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA. Electronic address: sidney.hecht@asu.edu.
authors.forename: Sidney M
authors.initials: SM
authors.lastname: Hecht
mesh_terms: D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry*; D014364:Tryptophan / Q000031:analogs & derivatives*
chemical_list: D005456:Fluorescent Dyes; D014364:Tryptophan; D013762:Tetrahydrofolate Dehydrogenase
keywords: Amino acid; FRET; Fluorescence; Protein biosynthesis; Tryptophan analogues