Exploiting luminescence spectroscopy to elucidate the interaction between sugar and a tryptophan residue in the lactose permease of Escherichia coli.

ABSTRACT: The crystal structure of the Escherichia coli lactose permease at 3.5 A with a bound substrate has been reported recently. The structure reveals the sugar-protein contacts, which include hydrophobic stacking between the galactopyranosyl ring of substrate and the indole side chain of Trp-151, as proposed previously. The nature of this interaction is studied here by exploiting the luminescence properties of Trp-151 in a mutant devoid of other tryptophan residues. The following phenomena are observed. (i) The fluorescence emission spectrum of Trp-151 and fluorescence-quenching experiments with water-soluble quenchers demonstrate that Trp-151 is in a hydrophilic environment. (ii) Substrate binding leads to a blue shift in the emission spectrum and reduction in accessibility to polar quenchers,

SUBMITTER: Vazquez-Ibar JL 

PROVIDER: S-EPMC240682 | biostudies-literature | 2003 Oct

REPOSITORIES: biostudies-literature