We FRET so You Don’t Have To: New Models of the Lipoprotein Lipase Dimer

Lipoprotein lipase
(LPL) is a dimeric enzyme that is responsible
for clearing triglyceride-rich lipoproteins from the blood. Although
LPL plays a key role in cardiovascular health, an experimentally derived
three-dimensional structure has not been determined. Such a structure
would aid in understanding mutations in LPL that cause familial LPL
deficiency in patients and help in the development of therapeutic
strategies to target LPL. A major obstacle to structural studies of
LPL is that LPL is an unstable protein that is difficult to produce
in the quantities needed for nuclear magnetic resonance or crystallography.
We present updated LPL structural models generated by combining disulfide
mapping, computational modeling, and data derived from single-molecule
Förster resonance energy transfer (smFRET). We pioneer the
technique of smFRET for use with LPL by developing conditions for
imaging active LPL and identifying positions in LPL for the attachment
of fluorophores. Using this approach, we measure LPL–LPL intermolecular
interactions to generate experimental constraints that inform new
computational models of the LPL dimer structure. These models suggest
that LPL may dimerize using an interface that is different from the
dimerization interface suggested by crystal packing contacts seen
in structures of pancreatic lipase.