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[摘要]：Plasmodium falciparum enolase (Pfen) is of photosynthetic lineage as evident from the presence of a plant like pentapeptide insert (104)EWGWS(108) in a highly conserved surface loop of the protein. Such a unique region which is absent in human enolase, constitutes an excellent target for inhibitor design, provided its essentiality for function could be demonstrated. A deletion Pfen lacking this insert was made and the effect of this deletion on activity and structure was assessed. Deletion of insert resulted in similar to 100-fold decrease in k(cat)/K-m and caused dissociation of dimeric form into monomers. Since the parasite enolase localizes oil the merozoite Surface and confers partial protection against malaria [I. Pal-Bhowmick, M. Mehta, I. Coppens, S. Sharma, G.K. Jaron, Infect. Immun. 75 (11) (2007) 5500-5008], the possibility of the insert being involved in protective response was examined. Serum from Pfen vaccinated mouse which showed prolonged survival to parasite challenge had negligible reactivity against deletion protein as compared to wild type enolase. These results indicate that the insert sequence is required for the full enolase activity and may Constitute the protective antigenic epitope in parasite enolase. (C) 2009 Elsevier Inc. All rights reserved. |
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