M.Ceolín, U.S.Colombo, M.C.Frate, M.E.Clerico, E.Anton and M.R.Ermácora (2000) Head-to-tail and side-by-side oligomerization of Human Carbonic Anhydrase: a SAXS study. International Journal of Biological Macromolecules 28 145

Head-to-tail and side-by-side oligomerization of human carbonic anhydrase II: a small angle X-ray scattering study.

Ceolin M, Colombo US, Frate MC, Clerico E, Anton E, Ermacora MR.

Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C.67, 1900, La Plata, Argentina.

Solvent-induced directional aggregation of human carbonic anhydrase II (hCA) was studied by small angle X-ray scattering and fluorescence and fourth-derivative ultraviolet absorption spectroscopy. We propose that hCA at 5 mg ml(-1) in pure water forms head-to-tail oligomers built up, on average, by four to five monomers. At higher protein concentrations, the oligomers associate pair-wise and side-by-side. Spectroscopic evidence suggests that the subunits forming the aggregates are tightly folded, but with a structure that differs, at least locally, from the native state. A more complex aggregation pattern was observed under solvent conditions that favor the removal of zinc from the enzyme-active site, conditions under which the subunits are significantly less compact than in water. hCA may provide a useful model to investigate the effects of additives and genetic manipulation on protein aggregation.