title: Effects of limited tryptic proteolysis of bovine neurophysins on molecular properties of hormone binding, self-association, and antigenicity.
abstract: Limited tryptic fragmentation of disulfide-intact bovine neurophysins I and II (NP-I and -II, respectively) has been found to cause selective disruption of both hormone binding and neurophysin self-association. Loss of binding interactions, measured as a loss of ability to stimulate retardation of 125I-labeled neurophysin on Met-Tyr-Phe-amino-butylaminoagarose, is complete within 3 h at 37 degrees C. Reverse-phase high-performance liquid chromatography (HPLC) analysis of tryptic digests of neurophysin I allows detection of two major protein products and the peptide fragment 1-8. Release of the latter N-terminal piece occurs at about the same rate as loss of binding interactions. Reverse-phase HPLC elution behavior before and after performic acid oxidation and amino acid composition of the protein products led to their identification as NP-I-(9-93) (the 9-93 sequence) and [des-19,20]NP-I-(9-93) (the 9-93 sequence with the dipeptide 19-20 missing) for the more rapidly and more slowly formed species, respectively. NP-I-(9-93), unlike intact neurophysin I, is not retarded strongly by either Met-Tyr-Phe-amino-butylaminoagarose or neurophysin II-Sepharose. In contrast, both NP-I-(9-93) and [des-19,20]NP-I-(9-93) are equally as effective as intact NP-I in binding neurophysin I antibodies. The role of amino-terminal residues in promoting hormone binding, self-association, and antigenic recognition interactions is considered.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D046911:Macromolecular Substances; D009481:Neurophysins / Q000276:immunology / Q000378:metabolism*; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D009481:Neurophysins; D014357:Trypsin