Telling the Future of Amphipols
(# 2008 by Francis Haraux)
In other respects, however, the current situation is quite frustrating, because some of the inroads
that have been made and some of the tools that have been developed at great pains have not been used to
the level one could have expected. Here also, I will take two examples. One of them is NMR. The
application of amphipols to solution-state NMR studies of membrane proteins has been validated more
than 10 years ago, and its advantages and limits carefully delimited. The usefulness of combining
solution NMR studies of amphipol-trapped membrane proteins with upstream amphipol-assisted protein
folding has been demonstrated by establishing the structure of a ligand bound to a previously inaccessible
G protein-coupled receptor. Deuterated and pH-insensitive amphipols have been developed in order to
facilitate these studies. The tools were there to seize, and yet they have not entered routine use. The same
could be said of using amphipols to fold membrane proteins. Their efficiency has been demonstrated on a
dozen different proteins, including half-a-dozen G protein-coupled receptors. If one considers that,
downstream, the use of amphipol-trapped proteins has been validated in such important fields as electron
microscopy, NMR, and crystallization following transfer to lipidic mesophases, one can be genuinely
surprised that no more investigators have taken the jump and exploited amphipol-assisted folding to
produce and study their target proteins. What are the reasons for the reluctance or slowness of some
communities to embrace these novel tools? We can probably discern three of them.
A first obstacle to a more rapid dissemination is the classical hesitation at the prospect of adding,
to the difficulties of any biological investigation, those of mastering a novel methodology. Handling
membrane proteins in detergent solutions has the well-deserved reputation of being a tricky business,
but it is also a well-trodden path, followed by two generations of membrane biochemists, and its
dangers and tricks can be felt as mapped and somewhat foreseeable. Having to understand the behavior
and master the use of bizarre, heterogeneous polymers before even collecting one’s first biological data
can be felt as dissuasive. Amphipol workshops are regularly organized, in which novice users can
make their first hands-on contact with amphipols under the guidance of experienced users. They have
certainly helped to lower this activation barrier, but, obviously, not efficiently enough.
684
Final Comments
(# 2008 by Francis Haraux)
In other respects, however, the current situation is quite frustrating, because some of the inroads
that have been made and some of the tools that have been developed at great pains have not been used to
the level one could have expected. Here also, I will take two examples. One of them is NMR. The
application of amphipols to solution-state NMR studies of membrane proteins has been validated more
than 10 years ago, and its advantages and limits carefully delimited. The usefulness of combining
solution NMR studies of amphipol-trapped membrane proteins with upstream amphipol-assisted protein
folding has been demonstrated by establishing the structure of a ligand bound to a previously inaccessible
G protein-coupled receptor. Deuterated and pH-insensitive amphipols have been developed in order to
facilitate these studies. The tools were there to seize, and yet they have not entered routine use. The same
could be said of using amphipols to fold membrane proteins. Their efficiency has been demonstrated on a
dozen different proteins, including half-a-dozen G protein-coupled receptors. If one considers that,
downstream, the use of amphipol-trapped proteins has been validated in such important fields as electron
microscopy, NMR, and crystallization following transfer to lipidic mesophases, one can be genuinely
surprised that no more investigators have taken the jump and exploited amphipol-assisted folding to
produce and study their target proteins. What are the reasons for the reluctance or slowness of some
communities to embrace these novel tools? We can probably discern three of them.
A first obstacle to a more rapid dissemination is the classical hesitation at the prospect of adding,
to the difficulties of any biological investigation, those of mastering a novel methodology. Handling
membrane proteins in detergent solutions has the well-deserved reputation of being a tricky business,
but it is also a well-trodden path, followed by two generations of membrane biochemists, and its
dangers and tricks can be felt as mapped and somewhat foreseeable. Having to understand the behavior
and master the use of bizarre, heterogeneous polymers before even collecting one’s first biological data
can be felt as dissuasive. Amphipol workshops are regularly organized, in which novice users can
make their first hands-on contact with amphipols under the guidance of experienced users. They have
certainly helped to lower this activation barrier, but, obviously, not efficiently enough.
684
Final Comments