Factors that control the reactivity of the interface cysteine of triosephosphate isomerase from Trypanosoma brucei and Trypanosoma cruzi

Reyes Vivas,  Horacio

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Título :	Factors that control the reactivity of the interface cysteine of triosephosphate isomerase from Trypanosoma brucei and Trypanosoma cruzi
Creador:	Reyes Vivas, Horacio
Nivel de acceso:	Open access
Palabras clave :	Cisteína - metabolismo Triosa-Fosfato Isomerasa - metabolismo Trypanosoma brucei brucei - enzimología Trypanosoma cruzi - enzimología Cysteine - metabolism Triose-Phosphate Isomerase - metabolism Trypanosoma brucei brucei - enzymology Trypanosoma cruzi - enzymology cysteine; triosephosphate isomerase; amino acid sequence; article; enzyme structure; nonhuman; pH; pKa; priority journal; structure analysis; Trypanosoma brucei; Trypanosoma cruzi; X ray analysis; Amino Acid Sequence; Amino Acid Substitution; Animals; Cysteine; Dimerization; Enzyme Activation; Enzyme Inhibitors; Glutamic Acid; Glutamine; Glycolates; Hydrogen-Ion Concentration; Leishmania mexicana; Methyl Methanesulfonate; Molecular Sequence Data; Mutagenesis, Site-Directed; Peptide Fragments; Proline; Protein Structure, Tertiary; Triose-Phosphate Isomerase; Trypanosoma brucei brucei; Trypanosoma cruzi; Trypanosoma; Trypanosoma brucei; Trypanosoma cruzi
Descripción :	The amino acid sequences and X-ray structures of homodimeric triosephosphate isomerase from the pathogenic parasites Trypanosoma brucei (TbTIM) and Trypanosoma cruzi (TcTIM) are markedly similar. In the two TIMs, the side Chain Of the only interface cysteine (Cysl4) of one subunit docks into loop 3 of the other subunit. This portion of the interface is also markedly similar in the two enzymes. Nonetheless, Cysl4 of TcTIM is nearly 2 orders of magnitude more susceptible to the thiol reagent methylmethane thiosulfonate (MMTS) than Cys14 of TbTIM. The causes of this difference were explored by measuring the second-order rate constant of inactivation by MMTS (k2) under various conditions. At pH 7.4, k2 in TcTIM is 70 times higher than in TbTIM. The difference decreases to 30 when the amino acid sequence of loop 3 and adjoining residues of TbTIM are conferred to TcTIM (triple mutant). The pKa values of the thiol group of the interface cysteine of TcTIM and the triple mutant were 0.7 pH unit lower than in TbTIM. Because this difference could account for the different sensitivity of the enzymes to thiol reagents, we determined the k2 of inactivation at equal levels of ionization of their interface cysteines. Under these conditions, the difference in k2 between TcTIM and TbTIM became 8-fold, whereas that of the triple mutant to TbTIM was 1.5 times. The substrate analogue phosphoglycolate did not modify the pKa of the thiol group of the interface, albeit it diminished the rate of its derivatization by MMTS. In the presence of phosphoglycolate, under conditions in which the interface cysteines of the enzymes had equal levels Of protonation, the difference in k2 Of TcTIM and TbTIM became smaller, whereas k2 of the triple mutant was almost equal to that of TbTIM. Thus, from measurements of the reactivity of the interface cysteine in various conditions, it was possible to obtain information on the factors that control the dynamics of a portion of the dimer interface.
Colaborador(es) u otros Autores:	Hernández Alcántara Gloria López Velázquez Gabriel Cabrera Nallely Pérez Montfort Tuena de Gómez Puyou Marietta Gómez Puyou Armando
Fecha de publicación :	2001
Tipo de publicación:	Artículo
Formato:	pdf
Identificador del Recurso :	10.1021/bi002619j
Fuente:	Biochemistry 40(10):3134 - 3140
URI :	http://repositorio.pediatria.gob.mx:8180/handle/20.500.12103/2428
Idioma:	eng
Aparece en las colecciones:	Artículos

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