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Inhibition of a Cathepsin L-Like Cysteine Protease by a Chimeric Propeptide-Derived Inhibitor

2005; American Chemical Society; Volume: 44; Issue: 31 Linguagem: Inglês

10.1021/bi047590o

1943-295X

Emmanuel Godat, Subrata Chowdhury, Fabien Lecaille, Maya Belghazi, Enrico O. Purisima, Gilles Lalmanach,

Antimicrobial Peptides and Activities

Like other papain-related cathepsins, congopain from Trypanosoma congolense is synthesized as a zymogen. We have previously identified a proregion-derived peptide (Pcp27), acting as a weak and reversible inhibitor of congopain. Pcp27 contains a 5-mer YHNGA motif, which is essential for selectivity in the inhibition of its mature form [Lalmanach, G., Lecaille, F., Chagas, J. R., Authié, E., Scharfstein, J., Juliano, M. A., and Gauthier, F. (1998) J. Biol. Chem. 273, 25112−25116]. In the work presented here, a homology model of procongopain was generated and subsequently used to model a chimeric 50-mer peptide (called H3-Pcp27) corresponding to the covalent linkage of an unrelated peptide (H3 helix from Antennapedia) to Pcp27. Molecular simulations suggested that H3-Pcp27 (pI = 9.99) maintains an N-terminal helical conformation, and establishes more complementary electrostatic interactions (Ecoul = −25.77 kcal/mol) than 16N-Pcp27, the 34-mer Pcp27 sequence plus the 16 native residues upstream from the proregion (Ecoul = 0.20 kcal/mol), with the acid catalytic domain (pI = 5.2) of the mature enzyme. In silico results correlated with the significant improvement of congopain inhibition by H3-Pcp27 (Ki = 24 nM), compared to 16N-Pcp27 (Ki = 1 μM). In addition, virtual alanine scanning of H3 and 16N identified the residues contributing most to binding affinity. Both peptides did not inhibit human cathepsins B and L. In conclusion, these data support the notion that the positively charged H3 helix favors binding, without modifying the selectivity of Pcp27 for congopain.