Localising individual atoms of tryptophan side chains in the metallo-β-lactamase IMP-1 by pseudocontact shifts from paramagnetic lanthanoid tags at multiple sites

• DOI: 10.5194/mr-3-1-2022
• Publication Date: 2022-01-04T08:01:50Z
• Authors: Henry W. Orton; Iresha D. Herath; Ansis Maleckis; Shereen Jabar; Monika Szabo; Bim Graham; Colum Breen; Lydia Topping; Stephen J. Butler; Gottfried Otting
• Keywords: Side chain

Abstract. The metallo-β-lactamase IMP-1 features a flexible loop near the active site that assumes different conformations in single crystal structures, which may assist substrate binding and enzymatic activity. To probe position of this loop, we labelled tryptophan residues with 7-13C-indole protein lanthanoid tags at three sites. magnetic susceptibility anisotropy (Δχ) tensors were determined by measuring pseudocontact shifts (PCSs) backbone amide protons. Δχ subsequently used to identify atomic coordinates side chains protein. PCSs sufficient determine location Trp28, is targeted our experiments, high accuracy. Its average showed barely significant changes response inhibitor captopril. It was found localisation spaces could be defined better accuracy including only paramagnetic ion for each tag tagging site. effect attributed shallow angle PCS isosurfaces tend intersect if generated sites are identical except ion.