Biomedical Engineering Reference
In-Depth Information
CHAPTER 4
Protein Structure Determination
using Sparse NMR Data
OLIVER F. LANGE
Department Chemie, Biomolecular NMR and Munich Center for Integrated
Protein Science, Technische Universit¨t M ¨ nchen, Garching and Institute of
Structural Biology, Helmholtz Zentrum M ¨ nchen, Neuherberg, Germany
E-mail: oliver.lange@tum.de
4.1 Introduction
Advances in hardware, sample preparation, pulse sequence development and
refinement techniques have enabled NMR to study systems in solution that
previously were in the exclusive realm of X-ray crystallography with immense
benefits for structural biology. NMR studies might succeed where crystal-
lisation or phasing of diffraction data fails and can be used to check crystal
structures for artefacts due to crystal packing, crystallisation additives or cryo-
temperatures. Moreover, NMR has the unique ability to probe dynamics and
to characterise lowly populated conformational states during binding
processes,
1-3
conformational transitions,
4-7
and protein folding.
8
Despite this
progress, NMR de novo structure determination on systems that exceed 20 kDa
in molecular weight remains challenging due to increased linewidth and
spectral crowding.
9-12
The linewidths increase with slower molecular tumbling,
and hence even pose a problem when only part of the biomolecule is NMR
visible, while other parts (binding partners, additional domains or detergent
micelles) are made NMR-invisible by deuteration. The major contribution to
fast relaxation in slow tumbling molecules is dipolar interaction between
1
H
1
His
and hence can be reduced by using proteins where the majority of
