Robinson LZ, Reixach N. Quantification of quaternary structure stability in aggregation-prone proteins under physiological conditions: the transthyretin case.
Biochemistry 2014;
53:6496-510. [PMID:
25245430 PMCID:
PMC4204887 DOI:
10.1021/bi500739q]
[Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
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The quaternary structure stability
of proteins is typically studied
under conditions that accelerate their aggregation/unfolding processes
on convenient laboratory time scales. Such conditions include high
temperature or pressure, chaotrope-mediated unfolding, or low or high
pH. These approaches have the limitation of being nonphysiological
and that the concentration of the protein in solution is changing
as the reactions proceed. We describe a methodology to define the
quaternary structure stability of the amyloidogenic homotetrameric
protein transthyretin (TTR) under physiological conditions. This methodology
expands from a described approach based on the measurement of the
rate of subunit exchange of TTR with a tandem flag-tagged (FT2) TTR counterpart. We demonstrate that subunit exchange of
TTR with FT2·TTR can be analyzed and quantified using
a semi-native polyacrylamide gel electrophoresis technique. In addition,
we biophysically characterized two FT2·TTR variants
derived from wild-type and the amyloidogenic variant Val122Ile TTR,
both of which are associated with cardiac amyloid deposition late
in life. The FT2·TTR variants have similar amyloidogenic
potential and similar thermodynamic and kinetic stabilities compared
to those of their nontagged counterparts. We utilized the methodology
to study the potential of the small molecule SOM0226, a repurposed
drug under clinical development for the prevention and treatment of
the TTR amyloidoses, to stabilize TTR. The results enabled us to characterize
the binding energetics of SOM0226 to TTR. The described technique
is well-suited to study the quaternary structure of other human aggregation-prone
proteins under physiological conditions.
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