Structure, interactions, surface activity, and function of Fish Type III antifreeze protein in solution

ANDRÉS G. SALVAY; GABEL, F; PUCCI, B.; SANTOS, J.; HOWARD, E. I.; EBEL, C.

Paris

Congreso; 2nd European Conference on Macromolecular Hydrodynamics to living cells, HYDROPROT 2011; 2011

Institut Pasteur, Paris

Antifreeze proteins (AFPs) are found in a variety of cold-adapted organisms allowing survives sub-zero temperatures. This action is carried out by preventing ice growth and recrystallization in internal fluids through binding AFPs to ice surfaces. Fish Type III antifreeze protein (AFPIII) is a prototypical globular AFP of 7 kDa which present a surface exposed to the solvent predominantly hydrophobic (1). The crystallographic structure of AFPIII obtained by X-ray and neutron diffraction exhibits a flat ice-binding surface formed by predominantly nonpolar residues (2). In this work we used analytical ultracentrifugation, analytical size-exclusion chromatography, dynamic light scattering, and small angle neutron scattering, to characterize the interactions, homogeneity, and structure of AFP III in solution. Our results show that AFPIII is highly soluble presenting weak repulsive interactions and does not aggregate even at high concentrations (3). Surface tension measurements show a propensity of AFPIII to localize at the air/water interface, but this surface activity is not correlated with any aggregation in the bulk (3). AFPIII presents a high surface activity at the air/water interface which increases as temperature increase. We conclude that, contrary to what occurs at the air/water interface, AFPIII does not form close packed adsorption layer at the ice surface. This behaviour may be related to the efficiency of the protein functionality observed at low concentrations. References: 1. Salvay, A.G., J. Santos, E.I. Howard. Electro-optical properties characterization of Fish Type III Antifreeze Protein. Journal of Biological Physics 33 : 389-397 (2007). 2. Howard, E.I. et al. Neutron structure of type III Antifreeze Protein allows the reconstruction of AFP-ice interface. Journal of Molecular Recognition 24 :724-732 (2011). 3. Salvay, A.G., F. Gabel, B. Pucci, J. Santos, E.I. Howard, C. Ebel. Structure and interactions of Fish Type III Antifreeze Protein in solution. Biophysical Journal 99 : 609-618 (2010).