Fragmentation of crystalline beta-haemocyanin of Helix pomatia with plasmin and trypsin. Location of the fragments in the polypeptide chain.

The action of plasmin on tenth molecules of beta C-haemocyanin of Helix pomatia at pH 8.2 yielded first a three-domain fragment P3 and a five-domain fragment P1 (present as a dimer at pH 8.2). Fragment P1 was further split by plasmin into a four-domain fragment P2 and a one-domain fragment P4 (also present as a dimer at pH 8.2). Trypsinolysis of P2 yielded T2 and fragment X, which was further split into T1C and T3. Fragments P3 and P4 corresponded respectively to the tryptic fragments T1A and T1B, also by their circular dichroic spectra. The determination of the N-terminal groups and the order of splitting allowed the location of the fragments in the polypeptide chain: P3 (a--c), P2 (d--g), P4 (h); T1A (a--c), T3 (d), T1C (e--f), T2 (g), T1B (h).