The
unitary hypothesis on the coupling of energy transduction
and its relevance to the modeling of mechanisms
Bennun, A.
The unitary hypothesis
postulates that energy transduction processes are mediated
by the dynamics of molecular structural changes, which integrate
the catalytic and the transducing mechanisms at the level
of the coupling factor ATPase. The organization of molecules
within defined structures imposes physicochemical constraints
on the external space of proteins. The internal space of an
enzyme, rather than being subject to a random distribution
of interacting forces, would therefore be modified within
defined space vectors by forces of scalar magnitude. Apart
from specific operative mechanisms, the molecular chemistry
of the proteins of a transducing system is not especially
subject to the random distribution of kinetic energy. Accordingly,
kinetic energy does not behave in the same way as it does
in an undifferentiable space. At the level of structural modifications,
therefore, heat, rather than being the result of molecular
collisions, is the result of inter- or intramolecular friction.
Translational, rotational, and vibrational kinetic energy,
rather than being random participants in structural changes,
become dynamically organized for specific rearrangements of
the inter - and intramolecular space. The physico¬chemical
changes that confer anisotropy are in turnover between the
system's initial and final conditions. Hence, oscillatory
modifications of the enzyme's active site maintain time-breaking
symmetry and vectorial kinetics. Although these processes
belong to the realm of chemistry, they are subject to inter-and
intramolecular vectorial relationships which may be tentatively
defined as molecular dynamics.
The intent of this communication is to elaborate a mechanistic
perspective of processes which by their complex and diverse
nature obscure the basic principles that operate within the
dynamics of molecular organizations. Con¬sequently, experimental
findings have been analyzed in search of physico¬chemical
forces that could be operative at the level of dynamic molecular
structures. The thermodynamics of transducing systems is discussed,
as well as a hypothesis on vectorial kinetics. The nature
of the participating forces is evaluated, and the modeling
of several transducing processes has been at-tempted. The
latter are descriptions based upon the available knowledge,
but they are intended only to illustrate the mechanics of
the forces postulated to operate in energy transduction.
Annals of the New York Academy of Sciences, 227, (1974), 116-145