The mechanism of interallelic complementation at the INO1 locus in yeast: immunological analysis of mutants

The ino1 locus of yeast has been demonstrated to be the structural gene for the repressible enzyme, L-myo-inositol-1-phosphate synthase (Donahue and Henry 1981 a). We have screened a large number of allelic representatives of the ino1 locus for the presence of protein which cross reacts with antibody produced in response to purified wild type inositol-1-phosphate synthase. Approximately 50% of all ino1 representatives screened by immunoprecipitation produce a protein of 62,000 molecular weight, identical in size to the wild type enzyme subunit. These mutants (termed crm+) were tested for expression of the 62,000 MW protein under conditions which are repressing for the wild type enzyme (greater than 25 μM exogenous inositol). The protein produced by the crm+ mutants, like the active enzyme in wild type yeast, is repressed in the presence of high levels of exogenous inositol. In addition, we have reassessed the interallelic complementation pattern observed among mutants at the ino1 locus. The entire pattern of interallelic complementation is temperature sensitive

Studies on Stibanate unresponsive isolates of Leishmania donovani

Visceral leishmaniasis, also known as kala-azar (KA) is generally caused by Leishmania donovani. Organic pentavalent antimonials (SbV) is the first line of treatment for KA. However, the number of KA patients unresponsive to treatment with Sb(V) is steadily increasing in India and elsewhere. The primary objective of this work is to determine the factor(s) associated with the rise of unresponsiveness. Analysis of the clonal population of parasites clearly indicated that wild type parasites isolated from KA patients who were clinically cured after treatment with Sb(V), were a mixture of resistant and sensitive cells. The resistant promastigotes were also resistant as amastigotes in vivo. It was further observed that Stibanate sensitive parasites can be made resistant to the drug by repeated passages in experimental animals followed by incomplete treatment with suboptimal doses of the drug. These results suggest that the steady rise in Sb(V) unresponsiveness of KA patients in India is due to infection with resistant parasites, generated as a result of irregular and often incomplete treatment of the patients

Monoclonal antibody affinity purification of a 78 kDa membrane protein of Leishmania donovani of Indian origin and its role in host–parasite interaction

Monoclonal antibodies were raised against pathogenic promastigotes of Leishmania donovani of Indian origin. Among these, one was used for immuno-affinity purification of a 78 kDa membrane protein present in both the amastigote and promastigote forms of the parasite. Results of immunoblot experiments with the anti-78 kDa antibody revealed that the protein was present only in parasites belonging to the L. donovani complex. The expression of the protein was observed to be the same during different phases of growth of the promastigotes. Therefore, the 78 kDa protein is neither stage-specific nor differentially regulated. Surface iodination and subcellular fractionation of the promastigotes indicated that the protein was localized on the cell surface. The 78 kDa protein was found to inhibit the binding of promastigotes to macrophages significantly, suggesting that it may play a role in the process of infection. Thus, here we report the purification of a surface protein of L. donovani of Indian origin, which may play an important role in the process of infection