The engine of ABC proteins

MDR1 protein (ABC-C1) Over Expression in Giardia Intestinalis Incubated with Albendazole and Nitazoxanide

BACKGROUND

Giardia intestinalis is a worldwide parasite. Drugs used for the treatment of giardiasis are metronidazole, albendazole and nitazoxanide. The development of drug resistance is an obstacle to the effective treatment. Resistance mechanisms in some parasites involve the participation of ATP-binding cassette (ABC) transporter superfamily.

PURPOSE

To find if the ATP-binding cassette genes are overexpressed in trophozoites treated with albendazole or nitazoxanide.

METHODS

A search for ATP-binding cassette genes in Giardia sequence database (GiardiaDB) was done and six genes were selected. Trophozoites treated with albendazole or nitazoxanide and the expression of these six ABC genes was quantitated by real-time RT-PCR. The ABC-C1 gene was selected, and a fragment cloned. The ABC-C1 protein was expressed, and polyclonal antibodies were elicited in mice to detect the protein in treated trophozoites, finally a docking analysis was performed for ABC-C1 and tizoxanide interaction.

RESULTS

Bioinformatics analysis showed that the ATP-binding cassette (ABC) topology is present in the six proteins. The qRT-PCR revealed that the ABC-C1 gene was overexpressed in cells incubated with nitazoxanide or albendazole. Confocal analysis showed that ABC-C1 protein levels increased in trophozoites with both treatments but was higher with nitazoxanide. The mark was detected heavily in the periphery of the cells. Using a docking analysis, it was found that the nitazoxanide metabolite, tizoxanide was docked close to the ATP-binding region as well as in the exit tunnel, located in the transmembrane region.

CONCLUSION

These findings in Giardia intestinalis, support the possible role of ABC-C1 in drug efflux.

Development of an ELISA using a recombinant P46-like lipoprotein for diagnosis of Mycoplasma pulmonis infection in rodents

Mycoplasma pulmonis is one of the most prevalent bacterial pathogens that infects laboratory mice and rats. To develop an M. pulmonis-specific antigen for serological diagnosis, we cloned the cDNA of P46-like lipoprotein (P46L), an M. pulmonis putative periplasmic protein. P46L is a homolog of P46, an M. hyopneumoniae antigen. We produced recombinant P46L fused to glutathione S-transferase (GST) in Escherichia coli. Immunoblot analysis revealed that sera from Mycoplasma-infected mice and rats contained anti-P46L antibodies. We developed an ELISA using the recombinant P46L-GST protein as an antigen. Thirteen of the 14 samples from rats naturally infected with M. pulmonis were determined to be positive according to the commercial ELISA (MONILISA Myco) and positive by our ELISA. Furthermore, 18/19 samples from mice experimentally infected with M. pulmonis were positive using our P46L-GST ELISA. In contrast, only 8/19 samples from infected mice were positive by the commercial ELISA. Our results indicate that P46L-GST was an appropriate antigen for developing a serological test to determine M. pulmonis infection in laboratory mice and rats.

L-Rhamnose transport is sugar kinase (RhaK) dependent in Rhizobium leguminosarum bv. trifolii

Strains of Rhizobium leguminosarum which are unable to catabolize l-rhamnose, a methyl-pentose sugar, are compromised in the ability to compete for nodule occupancy versus wild-type strains. Previous characterization of the 11-kb region necessary for the utilization of rhamnose identified a locus carrying catabolic genes and genes encoding the components of an ABC transporter. Genetic evidence suggested that the putative kinase RhaK carried out the first step in the catabolism of rhamnose. Characterization of this kinase led to the observation that strains carrying rhamnose kinase mutations were unable to transport rhamnose into the cell. The absence of a functional rhamnose kinase did not stop the transcription and translation of the ABC transporter components. By developing an in vitro assay for RhaK activity, we have been able to show that (i) RhaK activity is consistent with RhaK phosphorylating rhamnose and (ii) biochemical activity of RhaK is necessary for rhamnose transport.