Structural determinants for globin hexacoordination. A comparison between myoglobin and neuroglobin

LUCIANA CAPECE; MARCELO A. MARTI; AXEL BIDON-CHANAL; ALEJANDRO D. NADRA; F. JAVIER LUQUE; DARIO A. ESTRIN

Aarhus, Dinamarca

Congreso; XVth International Conference on Oxygen Binding and Sensing Proteins; 2008

University of Aarhus

<!-- @page { size: 21cm 29.7cm; margin: 2cm } P { margin-bottom: 0.21cm } --> We have studied high pressure effects on the 5c to 6c equilibrium in Ngb and Mb by means of MD dynamics techniques. Using Steered Molecular Dynamics (SMD) we have computed the free energy profiles for the transition in normal and high pressure (3 kbar) conditions for both proteins. In agreement with the observed experimental data our results show that for both proteins high pressure enhances hexacoordination. Based on the equilibrium and SMD trajectories analysis we have shown that in Ngb the shift in equilibrium arises due to an increase in the 6c to 5c transition barrier whereas in MB a destabilization of the 5c seems to be responsible for the effect. Our results also show that the main effect of high pressure is to reduce the protein mobility without altering the structure in a significant manner. Last but not least and in agreement with our previous results on Ngb our data support the idea that the 6c to 5c equilibrium in globins in controlled by the structure and dynamics of the CD loop. &amp;amp;lt;!-- @page { size: 21cm 29.7cm; margin: 2cm } P { margin-bottom: 0.21cm } --&amp;amp;gt;