The high stability of cruzipain against pH-induced inactivation is not dependent on its C-terminal domain.
Unlike mammalian lysosomal cysteine proteases, the trypanosomal cysteine protease cruzipain contains a 130-amino acid residue C-terminal domain, in addition to the catalytic domain, and it is stable at neutral pH. The endogenous (with C-terminal domain) and recombinant (without C-terminal domain) cruzipains exhibit similar stabilities at both acid (k(inac)=3.1x10(-3) s(-1) and 4.4x10(-3) s(-1) at pH 2.75 for endogenous and recombinant cruzipain, respectively) and alkaline pH (k(inac)=3.0x10(-3) s(-1) and 3. 7x10(-3) s(-1) at pH 9.15 for endogenous and recombinant cruzipain, respectively). The pH-induced inactivation, which is a highly pH dependent first order process, is irreversible and accompanied by significant changes of secondary and tertiary structure as revealed by circular dichroism measurements. The different stability of cruzipain as compared to related proteases, is therefore due mainly to the different number, nature and distribution of charged residues within the catalytic domain and not due to addition of the C-terminal domain.
Stoka
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V
Department of Biochemistry and Molecular Biology, J. Stefan Institute, Jamova 39, Sl-1000, Ljubljana, Slovenia.
Turk
B
B
McKerrow
J H
JH
Björk
I
I
Cazzulo
J J
JJ
Turk
V
V
D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D003546:Cysteine Endopeptidases / Q000737:chemistry*; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins; D011994:Recombinant Proteins / Q000737:chemistry; D055672:Static Electricity; D014349:Trypanosoma cruzi / Q000201:enzymology*
D015800:Protozoan Proteins; D011994:Recombinant Proteins; D003546:Cysteine Endopeptidases; C063214:cruzipain