Identification of the pH-dependent membrane anchor of carboxypeptidase E (EC 3.4.17.10)

L. D. Fricker, B. Das, R. H. Angeletti

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Abstract

Carboxypeptidase E (CPE), a peptide hormone-processing enzyme, is present within secretory granules in both a soluble form and a form which is membrane-bound at pH 5.5 but soluble at neutral pH. Antisera raised against a peptide corresponding to the predicted COOH-terminus of CPE bind to the membrane-associated form of CPE but not to the soluble form. This COOH-terminal region is predicted to form an amphiphilic α-helix, containing several pairs of hydrophobic residues separated by hydrophilic residues. Synthetic COOH-terminal peptides 11-24 residues in length are able to bind to bovine pituitary membranes and can be extracted by conditions that extract the membrane-bound form of CPE. The influence of pH on the membrane binding of a 21-residue COOH-terminal peptide is similar to the membrane binding of CPE: at pH values <6 the majority of the peptide is membrane-bound, while at pH values above 8 less than 20% is membrane-bound. Both the 21-residue COOH-terminal peptide and the purified membrane form of CPE, but not the soluble form, partition into Triton X-114 only at low pH (pH <6). Combined polar and hydrophobic interactions of the COOH-terminal peptide appear to be responsible for the reversible, pH-dependent association of CPE with membranes.

Original languageEnglish (US)
Pages (from-to)2476-2482
Number of pages7
JournalJournal of Biological Chemistry
Volume265
Issue number5
Publication statusPublished - Apr 2 1990

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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