title: Partial digestion of neurophysins with proteolytic enzymes: unusual interactions between bovine neurophysin II and chymotrypsin.
abstract: Bovine neurophysin II was partially digested by chymotrypsin and by chymotrypsin followed by carboxy-peptidase B to produce large fragments collectively representing deletions of residues 1-5 and 91-95. All such fragments were capable of binding peptides to the principal hormone-binding site of neurophysin with normal or near-normal affinity, indicating that residues 1-5 and 91-95 do not directly participate in binding. In addition, preliminary results with thermolysin-derived fragments suggested that residue 6 does not participate in peptide binding. During the course of chymotrypsin studies, it was demonstrated that bovine neurophysin II behaves as a transient competitive inhibitor of chymotrypsin; for neurophysin-peptide complexes, Ki congruent to 8 x 10(-6) M. This inhibition is dependent on neurophysin conformation and is relieved by the anomalous preferential splitting by chymotrypsin of Arg-Arg and Phe-Pro bonds near the carboxyl terminus of neurophysin II. It is suggested that this phenomenon might reflect the interaction of neurophysin II with a chymotrypsin-related enzyme in the pituitary. One approach used in the study of binding properties of proteolytically modified neurophysin was affinity chromatography; the preparation and properties of a conveniently prepared affinity column for neurophysin are described.
mesh_terms: D002846:Chromatography, Affinity / Q000379:methods; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009481:Neurophysins / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D009481:Neurophysins; D009842:Oligopeptides; D010446:Peptide Fragments; D002918:Chymotrypsin