Modulation of prohormone convertase 1/3 properties using site-directed mutagenesis

Endocrinology. 2010 Sep;151(9):4437-45. doi: 10.1210/en.2010-0296. Epub 2010 Jul 7.


Prohormone convertase (PC)1/3 and PC2 cleave active peptide hormones and neuropeptides from precursor proteins. Compared with PC2, recombinant PC1/3 exhibits a very low specific activity against both small fluorogenic peptides and recombinant precursors, even though the catalytic domains in mouse PC1/3 and PC2 share 56% amino acid sequence identity. In this report, we have designed PC2-specific mutations into the catalytic domain of PC1/3 in order to investigate the molecular contributions of these sequences to PC1/3-specific properties. The exchange of residues RQG(314) with the SY sequence present in the same location within PC2 paradoxically shifted the pH optimum of PC1/3 upward into the neutral range; other mutations in the catalytic domain had no effect. Although none of the full-length PC1/3 mutants examined exhibited increased specific activity, the 66-kDa form of the RQG(314)SY mutant was two to four times more active than the 66-kDa form of wild-type PC1/3. However, stable transfection of RQG(314)SY into PC12 cells did not result in greater activity against the endogenous substrate proneurotensin, implying unknown cellular controls of PC1/3 activity. Mutation of GIVTDA(243-248) to QPFMTDI, a molecular determinant of 7B2 binding, resulted in increased zymogen expression but no propeptide cleavage or secretion, suggesting that this mutant is trapped in the endoplasmic reticulum due to an inability to cleave its own propeptide. We conclude that many convertase-specific properties are attributable less to convertase-specific catalytic cleft residues than to convertase-specific domain interactions.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites / genetics
  • Blotting, Western
  • Catalytic Domain / genetics
  • Cell Line
  • Enzyme Assays
  • Humans
  • Hydrogen-Ion Concentration
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed / methods*
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism*
  • Neurotensin / metabolism
  • PC12 Cells
  • Proprotein Convertase 1 / chemistry
  • Proprotein Convertase 1 / genetics
  • Proprotein Convertase 1 / metabolism*
  • Proprotein Convertase 2 / genetics
  • Proprotein Convertase 2 / metabolism
  • Protein Precursors / metabolism
  • Rats
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Transfection


  • Mutant Proteins
  • Protein Precursors
  • proneurotensin
  • Neurotensin
  • Proprotein Convertase 1
  • Proprotein Convertase 2