Limited trypsinolysis of beta-haemocyanin of Helix pomatia. Characterization of the fragments and heterogeneity of the copper groups by circular dichroism.

A limited trypsinolysis of the tenths of beta-haemocyanin of Helix pomatia was performed at pH 8.2. The absorbance at 346 nm remained constant, indicating a preservation of the oxygen-binding sites. The five tryptic fragments were separated by chromatography on Sephadex G-100 and on DEAE-cellulose. They contained 2 Cu per 50000 daltons and showed different mobilities in agar electrophoresis. The molecular weights indicated that one fragment was constituted of three functional domains of about 50000 daltons, that two fragments were constituted of two domains, and two others of one domain. Twentieths of beta-haemocyanin seemed thus to be made up of 9 domains. The circular dichroic spectra of the fragments indicated the presence of two classes of copper groups according to their positive maximum at 455 or at 500 nm. The circular dichroic spectra also showed that no fragment could have originated from a larger one, confirming the presence of nine domains in the twentieths.