INVESTIGADORES
MURGIDA Daniel Horacio
congresos y reuniones científicas
Título:
Membrane Potential Control of Electron Shuttle and Peroxidase Activity of Heme Proteins in Biomimetic Systems
Autor/es:
MURGIDA, D. H.
Lugar:
Salta
Reunión:
Congreso; 3rd Latin American Protein Society Meeting; 2010
Resumen:
Electron transfer (ET) chains involved in
photosynthesis and aerobic respiration take place at the level of biological
membranes where protein complexes exert their function under the influence of
strong electric fields. Here we report a study on the influence of these fields
on the structure and ET dynamics of different heme soluble proteins (cyt-c;
cyt-b562, cyt-c6, iso-cyt-c) that act as electron
shuttles in photosynthetic and respiratory chains of different organisms. The
proteins are immobilized on nanostructured Ag electrodes coated with biomimetic
films that are designed depending on the surface properties of each redox
protein.1,2 Structure, ET kinetics and protein dynamics are studied
simultaneously by using two-colors time-resolved surface-enhanced resonance
Raman (TR-SERR) spectroelectrochemistry.2 The atomistic
interpretation of the experiments is guided by molecular dynamics (MD)
simulations and electron pathways calculations of the biomimetic complexes.
This powerful combination of theoretical and experimental methods provides a
detailed and consistent picture of the interfacial ET mechanisms.3
In each case it is concluded that the overall ET rates are determined by an
interplay of protein dynamics and tunneling probabilities at the different
conformations along the dynamics. In turn, protein dynamics is strongly
modulated by the interfacial electric field, as demonstrated by TR-SERR
experiments and MD simulations performed under different conditions. It is also
shown that sufficiently strong electric fields are able to induce reversible
and irreversible structural changes of the ferric proteins in the complexes,
which produce a dramatic down-shift of the reduction potentials ann gain of peroxidase function pesumably
involved in the early steps of apoptosis.
For the natural partner protein of most
cytochromes, i.e. the CuA center of cyt-c oxidase, local and global
electrostatics are also shown to be crucial in modulating reduction potentials,
reorganization energies and crucial structural features.
Based on these results it is hypothesized that
transmembrane potentials play a regulatory role in respiration and
photosynthesis via a feedback inhibition mechanism.