Molecular Events in Lamin B1 Homopolymerization: A
Biophysical Characterization
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Abstract
Lamin
B1 is one of the major constituents of the nuclear lamina,
a filamentous network underlying the nucleoplasmic side of the inner
nuclear membrane. Homopolymerization of lamin B1, coupled to the homotypic
and heterotypic association of other lamin types, is central to building
the higher order network pattern inside the nucleus. This in turn
maintains the mechanical and functional integrity of the lamina. We
have characterized the molecular basis of the self-association of
lamin B1 using spectroscopic and calorimetric methods. We report that
concentration dependent lamin B1 oligomerization involves significant
alterations in secondary and tertiary structures of the protein resulting
in fairly observable compaction in size. Comparison of the energetics
of the homotypic association of lamin B1 with that of lamin A reported
earlier led to the finding that lamin A oligomers had higher thermodynamic
stability. This leads us to conjecture that lamin B1 has less stress
bearing ability compared to lamin A