Double Tryptophan Exciton Probe to Gauge Proximal Side Chains in Proteins: Augmentation at Low Temperature

作者：Gasymov Oktay K^*; Abduragimov Adil R; Glasgow Ben J

来源：Journal of Physical Chemistry B, 2015, 119(10): 3962-3968.

DOI：10.1021/jp512864s

The circular dichroic (CD) exciton couplet between tryptophans and/or tyrosines offers the potential to probe diStances, within 10 A in ptoteins. The exciton effect has been used with native chroinophores in critical positions in a few proteins. Here, sitedirected mutagenesis created double ttyptophan probes for key sites of a protein (tear lipocalin). For tear lipocalin, the crystal and solution structures, are concordant in both apoand holo-form. Double ttyptophan substitutions were performed at sites that could probe conformation arid were likely within 10 angstrom. Far-IN CD spectra of dOuble Tip tnutants were performed With conttOls-that had noninteracting substituted tryptophans. LoW temperature (77 K) was tested for augmentation of the excitoh signal. Exciton coupling appeared with tryptophan substitutions at positions within loop A-B (28 and 34 33), between loop A-B (28) and strand G (103 and 105); as well aS between the strands B (35) arid C (56). The CD exciton couplet signals were amplified 3-5-fold at 77 K. The results were concordant with close distances in crystal and solution structures. The exciton couplets had functional, significance and correctly assigned the bolo-conformation. The methodology creates an effeetive amino acids in a variety of motifs.

• 出版日期2015-3-12