Open AccessBackbone assignments and conformational dynamics in the S. typhimurium tryptophan synthase α-subunit from solution-state NMR
Author(s) -
Varun V. Sakhrani,
E. Hilario,
Bethany G. Caulkins,
Mary Hatcher-Skeers,
Ли Фан,
Michael F. Dunn,
Leonard J. Mueller
Publication year - 2020
Publication title -
journal of biomolecular nmr
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 106
eISSN - 1573-5001
pISSN - 0925-2738
DOI - 10.1007/s10858-020-00320-2
Subject(s) - chemistry , tryptophan synthase , tryptophan , crystallography , protein subunit , allosteric regulation , chemical shift , dissociation constant , stereochemistry , titration , random coil , conformational change , nuclear magnetic resonance spectroscopy , crystal structure , atp synthase , enzyme , circular dichroism , biochemistry , receptor , amino acid , gene
Backbone assignments for the isolated α-subunit of Salmonella typhimurium tryptophan synthase (TS) are reported based on triple resonance solution-state NMR experiments on a uniformly 2 H, 13 C, 15 N-labeled sample. From the backbone chemical shifts, secondary structure and random coil index order parameters (RCI-S 2 ) are predicted. Titration with the 3-indole-D-glycerol 3'-phosphate analog, N-(4'-trifluoromethoxybenzenesulfonyl)-2-aminoethyl phosphate (F9), leads to chemical shift perturbations indicative of conformational changes from which an estimate of the dissociation constant is obtained. Comparisons of the backbone chemical-shifts, RCI-S 2 values, and site-specific relaxation times with and without F9 reveal allosteric changes including modulation in secondary structures and loop rigidity induced upon ligand binding. A comparison is made to the X-ray crystal structure of the α-subunit in the full TS αββα bi-enzyme complex and to two new X-ray crystal structures of the isolated TS α-subunit reported in this work.