Work

Efficient 15 N– 13 C Polarization Transfer by Third-Spin-Assisted Pulsed Cross-Polarization Magic-Angle-Spinning NMR for Protein Structure Determination

Year: 2018

Type: article

Abstract: We introduce a pulsed third-spin-assisted recoupling experiment that produces high-intensity long-range 15 N– 13 C cross peaks using low radiofrequency (rf) energy. This Proton-Enhanced Rotor-echo Short-Pulse IRradiATION Cross-Polarization ( PERSPIRATION CP) pulse sequence operates with the same principle as the Proton-Assisted Insensitive-Nuclei Cross-Polarization ( PAIN CP) experiment but uses only a fraction of the rf energy by replacing continuous-wave 13 C and 15 N irradiation with rotor-echo 90° pulses. Using formyl-Met–Leu–Phe (f-MLF) and β1 immunoglobulin binding domain of protein G (GB1) as model proteins, we demonstrate experimentally how PERSPIRATION CP polarization transfer depends on the CP contact time, rf power, pulse flip angle, and 13 C carrier frequency and compare the PERSPIRATION CP performance with the performances of PAIN CP, RESPIRATION CP, and SPECIFIC CP for measuring 15 N– 13 C cross peaks. PERSPIRATION CP achieves long-range 15 N– 13 C transfer and yields higher cross peak-intensities than that of the other techniques. Numerical simulations reproduce the experimental trends and moreover indicate that PERSPIRATION CP relies on 15 N– 1 H and 13 C– 1 H dipolar couplings rather than 15 N– 13 C dipolar coupling for polarization transfer. Therefore, PERSPIRATION CP is an rf-efficient and higher-sensitivity alternative to PAIN CP for measuring long-range 15 N– 13 C correlations, which are essential for protein resonance assignment and structure determination. Using cross peaks from two PERSPIRATION CP 15 N– 13 C correlation spectra as the sole distance restraints, supplemented with (φ, ψ) torsion angles obtained from chemical shifts, we calculated the GB1 structure and obtained a backbone root-mean-square deviation of 2.0 Å from the high-resolution structure of the protein. Therefore, this rf-efficient PERSPIRATION CP method is useful for obtaining many long-range distance restraints for protein structure determination.

Source: The Journal of Physical Chemistry B

DOI: 10.1021/acs.jpcb.8b06400

Authors: Martin D. Gelenter, Mei Hong

Institution: Massachusetts Institute of Technology

Language: English

Topic: Advanced NMR Techniques and Applications

Subfield: Spectroscopy

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funders: National Institutes of Health, National Institute of General Medical Sciences

Awards: G2153353313, Structures and Dynamics of Proton and Cation-Dependent Channels and Transporters, Structures and lipid interactions of curvature-inducing membrane peptides by NMR, G4305611965