High pressure stability of protein complexes studied by static and dynamic light scattering

Abstract

The high pressure dissociation of hemocyanin prepared from the lobster Homarus americanus and casein micelles from cow milk were observed by in situ light scattering. The hemocyanin dodecamer dissociated via a hexamer into monomers in a two-step three-species reaction. The influence of ligands and the effector l-lactate on the dissociation behavior was investigated. While no effect by carbon monoxide after exchanging the ligand oxygen was observed, the addition of the effector l-lactate led to a decrease in the pressure stability. Due to a trimer intermediate which was found to be stabilized by l-lactate, the dissociation reaction in the presence of the effector was analyzed by a three-step four-species reaction. In the case of casein micelles, a two-step dissociation mechanism was found. The stabilizing interactions of casein micelles were identified and separated.

Keywords:

• static and dynamic light scattering
• protein complexes
• ligand binding
• intermolecular interactions

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft: Forschergruppe FR 456/25-4, project A1+A4. The authors thank T. Nawroth for the helpful advice on gel chromatography, and W. Doster, J. Friedrich and A. Delgado for helpful suggestions and stimulating discussions.

Notes

^†This paper was presented at the 6^th International Conference on High Pressure Bioscience, Biotechnology (HPBB 2010), Freising (Germany), 28 August–1 September 2010.