AUTHOR=Zadorozhnyi Roman , Sarkar Sucharita , Quinn Caitlin M. , Zadrozny Kaneil K. , Ganser-Pornillos Barbie K. , Pornillos Owen , Gronenborn Angela M. , Polenova Tatyana 

TITLE=Determination of Histidine Protonation States in Proteins by Fast Magic Angle Spinning NMR

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=Volume 8 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2021.767040

DOI=10.3389/fmolb.2021.767040

ISSN=2296-889X

ABSTRACT=Histidine residues play important structural and functional roles in proteins, such as serving as metal-binding ligands, mediating enzyme catalysis, and modulating proton channel activity. Many of these activities are modulated by the ionization state of the imidazole ring. Here we present a fast MAS NMR approach for the determination of protonation and tautomeric states of His at frequencies of 40-62 kHz. The experiments combine 1H detection with selective magnetization inversion techniques and transferred echo double resonance (TEDOR) – based filters, in 2D heteronuclear correlation experiments. We illustrate this approach using microcrystalline assemblies of HIV-1 CACTD-SP1 protein.