Relationship between protein structural fluctuations and rebinding dynamics in ferric haem nitrosyls.

Neil T Hunt , Gregory M Greetham , Michael Towrie , Anthony W Parker , Nicholas P Tucker (1)

1 SIPBS

The interaction of nitric oxide (NO) with haem proteins is widespread in biology. Here, we present the first ultrafast 2D-IR spectroscopic analysis of haem nitrosylation, which has been combined with time-resolved infrared pump-probe studies to investigate the relationship between equilibrium vibrational dynamics of the haem environment and ligand rebinding behaviour following photolysis of NO from the FeIII-NO site. Studies of two haem proteins, myoglobin (Mb) and cytochrome-c (Cc), which play different physiological roles, reveal marked contrasts in the ultrafast fluctuations of the protein pockets containing the haem, showing that the Mb pocket is somewhat more flexible than that of Cc. This correlates strongly with slower observed photolysis rebinding kinetics of Mb-NO versus Cc-NO and indicates a direct link between ultrafast fluctuations and biological functionality. Further, this indicates the validity of linear response theories in relation to protein ligand binding. Finally, 2D-IR shows that Cc-NO displays two distinct structural sub sites at room temperature that do not exchange on the timescales accessible via the NO vibrational lifetime.

Mots clés: Life Sciences

Neil T Hunt, Gregory M Greetham, Michael Towrie, Anthony W Parker, Nicholas P Tucker. Relationship between protein structural fluctuations and rebinding dynamics in ferric haem nitrosyls.. Biochemical Journal, 2011, 433 (3), pp.459-468. ⟨10.1042/BJ20101496⟩. ⟨hal-00558098⟩