Biomedical Engineering Reference
In-Depth Information
CHAPTER 12
NMR of Membrane Proteins
MARK BOSTOCK AND DANIEL NIETLISPACH*
Department of Biochemistry, University of Cambridge, 80 Tennis Court
Road, Cambridge, CB2 1GA, UK
*E-mail: dn206@bioc.cam.ac.uk
12.1 Introduction
Membrane proteins are predicted to make up approximately one-third of
proteins in the genome,
1
however, to date they remain significantly structurally
under-represented, with unique structures comprising only 0.4% of all PDB-
deposited structures.
2,3
Nevertheless these figures must be set against a recent
surge in structures of membrane proteins, including mammalian proteins,
4
following a predicted exponential trend.
5,6
Whilst many of these structures
have been solved by X-ray crystallography, NMR has also contributed a
significant number,
7
currently 16%.
8
Considerable progress has also been made
in the field of solid-state NMR,
9-11
however, in this review we focus on
solution-state NMR. In particular, a number of recent structures demonstrate
that solution NMR is able to tackle a range of large membrane proteins up to
around y100 kDa. b-Barrel proteins
12-15
remain easier to study because their
secondary structure allows orientational information to be obtained through
hydrogen bonds and short-range NOEs between adjacent strands. Recently,
NMR has also proved able to study a range of large a-helical membrane
proteins,
16-19
demonstrating that the technology has matured to a level at
which membrane protein structure determination by NMR can be considered a
viable approach.
Significant limitations still remain, in particular in the realm of sample
preparation. Although a number of expression systems are available and their
