The Monod-Wyman-Changeux allosteric model accounts for the quaternary transition dynamics in wild type and a recombinant mutant human hemoglobin

International audience; The acknowledged success of the Monod-Wyman-Changeux (MWC) allosteric model stems from its efficacy in accounting for the functional behavior of many complex proteins starting with hemoglobin (the paradigmatic case) and extending to channels and receptors. The kinetic aspects of the allosteric model, however, have been often neglected, with the exception of hemoglobin and a few other proteins where conformational relaxations can be triggered by a short and intense laser pulse, and monitored by time-resolved optical spectroscopy. Only recently the application of time-resolved wide-angle X-ray scattering (TR-WAXS), a direct structurally sensitive technique, unveiled th…

Tracking hemoglobin structural dynamics: from dilute solutions to intact cells

Probing protein structural dynamics in a human cell

Probing in cell protein structural changes with time-resolved X-ray scattering

International audience; Investigating protein structural changes inside the cell is a major goal in molecular biology. Here we show that time-resolved wide-angle X-ray scattering is a valuable tool for this purpose. Hemoglobin has been chosen as a model system and its tertiary and quaternary conformational changes following laser flash-photolysis have been tracked in intact red blood cells with nanosecond time resolution.

Conformational substates of ferricytochrome c revealed by combined optical absorption and electronic circular dichroism spectroscopy at cryogenic temperature.

We have investigated the heterogeneity of the Fe(III)–Met80 linkage of horse heart ferricytochrome c by probing the 695 nm charge transfer band with absorption and electronic circular dichroism (ECD) spectroscopy. In order to verify the connection between conformational substates of the Fe(III)–Met80 linkage and the 695 nm band spectral heterogeneity, we have performed experiments as a function of pH (neutral and acidic) and temperature (room and 20 K). At room temperature, the ECD spectrum is blue shifted with respect to the absorption one; the shift is more pronounced at acidic pH and is compatible with the presence of sub-bands. ECD measurements at 20 K highlighted the heterogeneous natu…