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Characterisation of benzimidazole binding with recombinant tubulin from Giardia duodenalis, Encephalitozoon intestinalis, and Cryptosporidium parvum.

Abstract：

:The binding kinetics of several benzimidazole compounds were determined with recombinant tubulin from benzimidazole-sensitive and -insensitive organisms. This study utilised the naturally occurring high efficacy of the benzimidazoles for the parasitic protozoa Giardia duodenalis and Encephalitozoon intestinalis, and low efficacy with Cryptosporidium parvum. Direct kinetic analysis of the benzimidazole-beta-tubulin interaction was performed using a fluorescence-based quenching method to determine the apparent association (k(on)) and dissociation (k(off)) rate constants from which the affinity constant (K(a)) was calculated. The binding kinetics were determined with recombinant alpha- and beta-tubulin from the parasitic protozoa with several benzimidazole R(2)-carbamate analogues. The affinity constant for the binding of several benzimidazoles with beta-tubulin from benzimidazole-sensitive protozoa was found to be significantly greater than binding to beta-tubulin from benzimidazole-insensitive protozoa. Additionally, the high affinity of several benzimidazole derivatives (albendazole, fenbendazole, mebendazole) for monomeric beta-tubulin and heterodimeric alphabeta-tubulin from benzimidazole-sensitive protozoa was also clearly demonstrated. The affinity constants determined with beta-tubulin from G. duodenalis and E. intestinalis also supported the observed in vitro efficacy of these compounds. The binding characteristics of the benzimidazoles with the highest in vitro efficacy (albendazole, fenbendazole, mebendazole) was reflected in their high association and slow dissociation rates with the beta-tubulin monomer or dimer from benzimidazole-sensitive protozoa compared with insensitive ones. Benzimidazole-bound alphabeta-tubulin heterodimers also had a significantly lower rate of microtubule assembly compared with benzimidazole-free alphabeta-heterodimers. The incorporation of benzimidazole-bound alphabeta-heterodimers into assembling microtubules was shown to arrest polymerisation in vitro although the addition of benzimidazole compounds to assembled microtubules did not result in depolymerisation. These findings indicate that a benzimidazole-beta-tubulin cap may be formed at the growing end of the microtubule and this cap prevents elongation of the microtubule.

journal_name

Mol Biochem Parasitol

journal_title

Molecular and biochemical parasitology

authors

MacDonald LM,Armson A,Thompson AR,Reynoldson JA

doi

10.1016/j.molbiopara.2004.08.001

subject

Has Abstract

pub_date

2004-11-01 00:00:00

pages

89-96

issue

eissn

0166-6851

issn

1872-9428

pii

S0166-6851(04)00214-2

journal_volume

138

pub_type

杂志文章

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Characterisation of benzimidazole binding with recombinant tubulin from Giardia duodenalis, Encephalitozoon intestinalis, and Cryptosporidium parvum.