Molecular motors are little systems in which one molecule moves accros a potential landscape. For instance,
- the ribosome moving
along the messenger RNA.
- the RNA polymerase moving along the DNA strand.
- Myosin moving along actin filaments.
Nowadays biological molecular
motors are highly efficient and complicated systems. However, most likely at the beginning of life (when the prebiotic and
protobiotic processes were taking place and the first biological molecules were synthetized), the primitive versions of these
molecular motors were much simpler than they are today. For instance, think of the ribosome. Ribosomes are very complex macromolecules
that carry out very complicated tasks. One might argue that this complexity is the result of millions of years of evolution. However,
can we imagine a primitive version of a ribosome? What would its properties have been? How simple a ribosome can be to still
be considered as a ribosome?
One of my research interests consists in elucidating how these biological molecular motors
started in the first place, giving rise to the prebiotic and protobiotic processes that eventually led to the origing of living organisims.
Cocho, Gustavo Martinez-Mekler, Hernan Larralde and I put forward a model of a "primitive ribosome" moving along a
messenger RNA. The model is indeed very simple: the ribosome is represented by a charged particle and the messenger RNA
by a polymer made up of charged monomers. Uncer very general conditions, we find that, when the particle is driven by an external
force, it moves along the polymer in steps whose average length is three monomers. THREE MONOMERS!! Does that ring a bell? Surely
it does. Codons, the fundamental information units of the genetic code, are made up of three monomers. With a
simple dynamical model we can gain insight about the three-base codon structure of the genetic code, beyond the traditional
argument given by Brenner about the "optimal" number of bases to specify 20 aminoacids.
This work, which I really like,
can be found here.
Computer reconstruction of an RNA polymerase moving along a DNA thread (in blue) and producing RNA (red strand).