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Updated: Jul 28, 2026

Study of Protein Dynamics via Neutron Spin Echo Spectroscopy
Published on: April 13, 2022
Cavities and packing defects in the structural dynamics of myoglobin
1Istituto Pasteur-Fondazione Cenci Bolognetti and Department of Biochemical Sciences A. Rossi Fanelli', University of Rome La Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy. maurizio.brunori@uniroma1.it
Abstract:
Small globular proteins contain internal cavities and packing defects that reduce thermodynamic stability but seem to play a role in controlling function by defining pathways for the diffusion of the ligand/substrate to the active site. In the case of myoglobin (Mb), a prototype for structure-function relationship studies, the photosensitivity of the adduct of the reduced protein with CO, O2 and NO allows events related to the migration of the ligand through the matrix to be followed. The crystal structures of intermediate states of wild-type (wt) and mutant Mbs show the photolysed CO to be located either in the distal heme pocket (primary docking site) or in one of two alternative cavities (secondary docking sites) corresponding to packing defects accessible to an atom of xenon. These results convey the general picture that pre-existing internal cavities are involved in controlling the dynamics and reactivity of the reactions of Mb with O2 and other ligands, including NO.
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