J. Biol. Chem., Vol. 261, Issue 23, 10606-10609, Aug, 1986
Independent refolding of domains in the pancreatic serine proteinases
JN Higaki and A Light
Ser-neotrypsinogen and Val-neotrypsinogen are two-chain modifications of
bovine trypsinogen produced on limited proteolysis with trypsin. Ser-
neotrypsinogen has Lys131-Ser132 cleaved in the connecting peptide (the
autolysis loop) linking the amino- and carboxyl-terminal domains. Val-
neotrypsinogen has Arg105-Val106 cleaved which is located within the
amino-terminal domain. The mixed disulfide derivative of Ser-
neotrypsinogen was successfully refolded. A functional molecule was
regenerated from the polypeptide fragments with the correct molecular
weight of neotrypsinogen in an overall yield of 7%. Val-Neotrypsinogen
could not be refolded. The first-order rate constants for the regeneration
of Ser-neotrypsinogen were determined from the formation of active enzyme
molecules as a function of time and from the regain of the correct
molecular weight. Both kinetic values were the same indicating that
refolding of the polypeptide chains first forms globular domain structures.
The two domains then associate and the disulfide bonds between the domains
and the correct geometry of the active site residues are formed last. The
same kinetic results were also found in refolding Thr-neochymotrypsinogen
(Duda, C. T., and Light, A. (1982) J. Biol. Chem. 257, 9866-9871) where
peptide bond cleavage also occurred in the connecting peptide. These
observations support the hypothesis that the pathway of folding of serine
proteinases proceeds with the independent refolding of domains.