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doi:10.1016/0166-6851(91)90216-S 
Copyright © 1991 Published by Elsevier B.V.
Self-proteolysis of the cysteine proteinase, cruzipain, from Trypanosoma cruzi gives a major fragment corresponding to its carboxy-terminal domain
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Received 3 May 1990;
Abstract
The major cysteine proteinase (cruzipain) purified from Trypanosoma cruzi epimastigotes catalyzes its own degradation in the presence of β-mercaptoethanol, at 56°C and pH 6. The reaction is affected by the same inhibitors which inhibit the azocaseinase activity, and yields a major 25-kDa fragment, which contains carbohydrate, few, if any, aromatic amino acids, and presents a proline-rich N-terminus (GPGPXPEP…), in addition to a number of small peptides, which can be isolated by reversed-phase HPLC, but are lost during electrophoresis. The results, together with recently published evidence of Mottram et al. and Eakin et al., are compatible with a structure for cruzipain consisting of a conventional cysteine proteinase moiety, linked to a long C-terminal extension including the 25-kDa fragment, which would contain a high proportion of the carbohydrate and the proline residues present in the original 60-kDa molecule.
Keywords: Trypanosoma cruzi; Cysteine proteinase; Cruzipain; Self-proteolysis
Abbreviations: HPLC, high performance liquid chromatography; PVDF, polyvinylidene difluoride; PTH, phenyl thiohydantoin; TFSM, trifluoromethane sulfonic acid; E-64, trans-epoxysuccinyl-L-leucylamido (4-guanidino)butane; TLCK, tosyl-lysyl-chloromethyl ketone; TPCK, tosyl-phenylalanyl-chloromethyl ketone; PMSF, phenyl methyl sulfonyl fluoride
