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Two Histidines in an α‐Helix: A Rigid Co 2+ ‐Binding Motif for PCS Measurements by NMR Spectroscopy
Author(s) -
Bahramzadeh Alireza,
Jiang Hailun,
Huber Thomas,
Otting Gottfried
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201802501
Subject(s) - nuclear magnetic resonance spectroscopy , spectroscopy , chemistry , crystallography , helix (gastropod) , motif (music) , stereochemistry , nuclear magnetic resonance , physics , biology , ecology , quantum mechanics , snail , acoustics
Pseudocontact shifts (PCS) generated by paramagnetic metal ions present valuable long‐range information in the study of protein structural biology by nuclear magnetic resonance (NMR) spectroscopy. Faithful interpretation of PCSs, however, requires complete immobilization of the metal ion relative to the protein, which is difficult to achieve with synthetic metal tags. We show that two histidine residues in sequential turns of an α‐helix provide a binding site for a Co 2+ ion, which positions the metal ion in a uniquely well‐defined and predictable location. Exchange between the bound and free cobalt is slow on the timescale defined by chemical shifts, but the NMR resonance assignments are nonetheless readily transferred from the diamagnetic to the paramagnetic NMR spectrum by an I z S z ‐exchange experiment. The double‐histidine‐Co 2+ motif offers a straightforward, inexpensive, and convenient way of generating precision PCSs in proteins.