Changing the inhibitory specificity and function of cucurbita maxima trypsin inhibitor-V by site-directed mutagenesis

Lisa Wen, In suk Lee, Guojin J. Chen, Jenq Kuen Huang, Yu Xi Gong, Ramaswamy Krishnamoorthi

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Cucurbita maxima trypsin inhibitor-V (CMTI-V) is also a specific inhibitor of human blood coagulation factor β-factor XIIa. A recombinant version of CMTI-V has allowed probing of roles of individual amino acid residues including the reactive site residue, lysine (P1), by site-directed mutagenesis. The K44R showed at least a 5-fold increase in inhibitory activity toward human β-factor XIIa, while there was no change toward bovine trypsin. This result demonstrates that β-factor-XIIa prefers an arginine residue over lysine residue, while trypsin is non-specific to lysine or arginine in its binding pocket. On the other hand, the specificity of CMTI-V could be changed from trypsin to chymotrypsin inhibition by mutation of the P1 residue to either leucine or methionine (K44L or K44M).

Original languageEnglish
Pages (from-to)897-902
Number of pages6
JournalBiochemical and Biophysical Research Communications
Issue number3
Publication statusPublished - 1995 Feb 27


All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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