Nuclear Magnetic Resonance Studies of
Amphipol-Trapped Membrane Proteins 10
Summary
Because they stabilize most membrane proteins as compared to detergent solutions and
they trap them under the form of small particles, amphipols (APols) appear as an
attractive potential medium for solution-state NMR (sNMR) studies. sNMR studies of
APol-trapped membrane proteins have yielded information on the conformation of the
proteins, their areas of contact with the polymer, their dynamics, their accessibility to
water, and the structure of protein-bound ligands. They have benefited from the
diversification of APol chemical structures and the availability of deuterated APols.
The advantages and constraints of working with APols are discussed and compared to
those associated with other nonconventional media.
10.1 Introduction
Nuclear magnetic resonance (NMR) is, along with X-ray crystallography (Chap. 11) and electron
microscopy (EM; Chap. 12), one of the three techniques that can provide an exhaustive description of
the three-dimensional (3D) arrangement of atoms in biological macromolecules and, thereby, help
understand their structure and function. The application of NMR to membrane proteins (MPs), while
fraught with difficulties, has been progressing in a spectacular manner since the late 1990s to the early
2000s, when the first NMR structures of MPs were established (MacKenzie et al. 1997; Arora et al.
2001; Fernández et al. 2001a, b). Whereas much of the present chapter will be concerned with the
challenges and opportunities of using APols for establishing complete structures of MPs by solution
NMR, it would be misleading to limit to this particular application the contributions that NMR can
make to understanding MPs. NMR signals are sensitive to the distance between nuclei and to the
dynamics of their interactions, and they are usually collected at or slightly above room temperature,
rather than on frozen samples as most X-ray and EM data are. They can therefore be exploited to derive
information that neither X-ray crystallography nor EM can, or can easily, provide, such as conformational equilibria and the changes they undergo upon ligand binding, the 3D structure of a ligand bound
to a non-crystallizable receptor, interactions with the membrane environment, etc. Such information
can be more easily accessible than establishing de novo by NMR a whole MP structure, and it brings
information that is complementary to that yielded by other approaches.
# Springer International Publishing AG, part of Springer Nature 2018
J. -L. Popot, Membrane Proteins in Aqueous Solutions, Biological and Medical Physics,
Biomedical Engineering, https://doi.org/10.1007/978-3-319-73148-3_10
453
Amphipol-Trapped Membrane Proteins 10
Summary
Because they stabilize most membrane proteins as compared to detergent solutions and
they trap them under the form of small particles, amphipols (APols) appear as an
attractive potential medium for solution-state NMR (sNMR) studies. sNMR studies of
APol-trapped membrane proteins have yielded information on the conformation of the
proteins, their areas of contact with the polymer, their dynamics, their accessibility to
water, and the structure of protein-bound ligands. They have benefited from the
diversification of APol chemical structures and the availability of deuterated APols.
The advantages and constraints of working with APols are discussed and compared to
those associated with other nonconventional media.
10.1 Introduction
Nuclear magnetic resonance (NMR) is, along with X-ray crystallography (Chap. 11) and electron
microscopy (EM; Chap. 12), one of the three techniques that can provide an exhaustive description of
the three-dimensional (3D) arrangement of atoms in biological macromolecules and, thereby, help
understand their structure and function. The application of NMR to membrane proteins (MPs), while
fraught with difficulties, has been progressing in a spectacular manner since the late 1990s to the early
2000s, when the first NMR structures of MPs were established (MacKenzie et al. 1997; Arora et al.
2001; Fernández et al. 2001a, b). Whereas much of the present chapter will be concerned with the
challenges and opportunities of using APols for establishing complete structures of MPs by solution
NMR, it would be misleading to limit to this particular application the contributions that NMR can
make to understanding MPs. NMR signals are sensitive to the distance between nuclei and to the
dynamics of their interactions, and they are usually collected at or slightly above room temperature,
rather than on frozen samples as most X-ray and EM data are. They can therefore be exploited to derive
information that neither X-ray crystallography nor EM can, or can easily, provide, such as conformational equilibria and the changes they undergo upon ligand binding, the 3D structure of a ligand bound
to a non-crystallizable receptor, interactions with the membrane environment, etc. Such information
can be more easily accessible than establishing de novo by NMR a whole MP structure, and it brings
information that is complementary to that yielded by other approaches.
# Springer International Publishing AG, part of Springer Nature 2018
J. -L. Popot, Membrane Proteins in Aqueous Solutions, Biological and Medical Physics,
Biomedical Engineering, https://doi.org/10.1007/978-3-319-73148-3_10
453