Jump to main content
Jump to site search

Issue 8, 2016
Previous Article Next Article

Quantitative evaluation of positive ϕ angle propensity in flexible regions of proteins from three-bond J couplings

Author affiliations

Abstract

3 J HNHα and 3JC′C′ couplings can be readily measured in isotopically enriched proteins and were shown to contain precise information on the backbone torsion angles, ϕ, sampled in disordered regions of proteins. However, quantitative interpretation of these couplings required the population of conformers with positive ϕ angles to be very small. Here, we demonstrate that this restriction can be removed by measurement of 3JC′Hα values. Even though the functional forms of the 3JC′Hα and 3JHNHα Karplus equations are the same, large differences in their coefficients enable accurate determination of the fraction of time that positive ϕ angles are sampled. A four-dimensional triple resonance HACANH[C′] E.COSY experiment is introduced to simultaneously measure 3JC′Hα and 3JHNC′ in the typically very congested spectra of disordered proteins. High resolution in these spectra is obtained by non-uniform sampling (in the 0.1–0.5% range). Application to the intrinsically disordered protein α-synuclein shows that while most residues have close-to-zero positive ϕ angle populations, up to 16% positive ϕ population is observed for Asn residues. Positive ϕ angle populations determined with the new approach agree closely with consensus values from protein coil libraries and prior analysis of a large set of other NMR parameters. The combination of 3JHNC′ and 3JC′C′ provides information about the amplitude of ϕ angle dynamics.

Graphical abstract: Quantitative evaluation of positive ϕ angle propensity in flexible regions of proteins from three-bond J couplings

Back to tab navigation

Supplementary files

Publication details

The article was received on 31 Jul 2015, accepted on 21 Sep 2015 and first published on 21 Sep 2015


Article type: Paper
DOI: 10.1039/C5CP04542H
Author version
available:
Download author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2016,18, 5759-5770
  •   Request permissions

    Quantitative evaluation of positive ϕ angle propensity in flexible regions of proteins from three-bond J couplings

    J. H. Lee, J. Ying and A. Bax, Phys. Chem. Chem. Phys., 2016, 18, 5759
    DOI: 10.1039/C5CP04542H

Search articles by author

Spotlight

Advertisements