Remarked Suppression of Aβ 42 Protomer-Protomer Dissociation Reaction
Elucidated by Molecular Dynamics Simulation
Abstract
Multimeric protein complexes are molecular apparatuses to regulate
biological systems and often determine their fate. Among proteins
forming such molecular assemblies, amyloid proteins have drawn attention
over a half-century since amyloid fibril formation of these proteins is
supposed to be a common pathogenic cause for neurodegenerative diseases.
This process is triggered by the accumulation of fibril-like aggregates,
while the microscopic mechanisms are mostly elusive due to technical
limitation of experimental methodologies in individually observing each
of diverse aggregate species in the aqueous solution. We then addressed
this problem by employing atomistic molecular dynamics simulations for
the paradigmatic amyloid protein, amyloid-β (1-42) (Aβ
42). Seven different dimeric forms of oligomeric Aβ
42 fibril-like aggregate in aqueous solution, ranging
from tetramer to decamer, were considered. We found additive effects of
the size of these fibril-like aggregates on their thermodynamic
stability and have clarified kinetic suppression of protomer-protomer
dissociation reactions at and beyond the point of pentamer dimer
formation. This observation was obtained from the specific combination
of the Aβ 42 protomer structure and the physicochemical
condition that we here examined, while it is worthwhile to recall that
several amyloid fibrils take dimeric forms of their protomers. We could
thus conclude that the stable formation of fibril-like protomer dimer
should be involved in a turning point where rapid growth of amyloid
fibrils is triggered.