title: The role of conserved residues of chagasin in the inhibition of cysteine peptidases.
abstract: We have evaluated the roles of key amino acids to the action of the natural inhibitor chagasin of papain-family cysteine peptidases. A W93A substitution decreased inhibitor affinity for human cathepsin L 100-fold, while substitutions of T31 resulted in 10-100-fold increases in the K(i) for cruzipain of Trypanosoma cruzi. A T31A/T32A double mutant had increased affinity for cathepsin L but not for cruzipain, while the T31-T32 deletion drastically affected inhibition of both human and parasite peptidases. These differential effects reflect the occurrence of direct interactions between chagasin and helix 8 of cathepsin L, interactions that do not occur with cruzipain.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G, C.C.S., Cidade Universitária, Ilha do Fundão, Rio de Janeiro, 21949-900 RJ, Brazil.
authors.forename: Flavia C G
authors.initials: FC
authors.lastname: dos Reis
authors.forename: Brian O
authors.initials: BO
authors.lastname: Smith
authors.forename: Camila C
authors.initials: CC
authors.lastname: Santos
authors.forename: Tatiana F R
authors.initials: TF
authors.lastname: Costa
authors.forename: Julio
authors.initials: J
authors.lastname: Scharfstein
authors.forename: Graham H
authors.initials: GH
authors.lastname: Coombs
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Mottram
authors.forename: Ana Paula C A
authors.initials: AP
authors.lastname: Lima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D017931:DNA Primers; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D014349:Trypanosoma cruzi / Q000201:enzymology
chemical_list: D015853:Cysteine Proteinase Inhibitors; D017931:DNA Primers; D015800:Protozoan Proteins; C435145:chagasin, Trypanosoma