Adenosine Kinase Reactivation by Leishmania donovani Coded Cyclophilin and its Truncated Form
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
View Archive Info| Field | Value | |
| Title |
Adenosine Kinase Reactivation by Leishmania donovani Coded Cyclophilin and its Truncated Form
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| Creator |
Mukherjee, Debalina
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| Subject |
Structural Biology & Bioinformatics
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| Description |
Trypanosomatid parasites, that cause various neglected human diseases, have deadly effects on several million people worldwide. Visceral leishmaniasis or kala-azar, one of the disastrous trypanosomatid diseases, is spread by Leishmania donovani. L. donovani, a purine auxotroph, incapable of synthesizing purine bases de novo, fulfill the requirement of purines by salvaging purines from the host using its purine salvage pathway. Adenosine kinase, a key enzyme of this salvage pathway, phosphorylates adenosine to AMP. Previous reports from this laboratory suggested that AdK has an inherent tendency to form soluble aggregates, leading to inactivation of the enzyme. Further studies showed that a single domain cycliphilin (LdCyP) from L. donovani disrupted the aggregates with concomitant reactivation of the enzyme. The work presented in this dissertation revealed that ADP, one of the products of AdK
reaction, facilitated aggregate formation. These ADP-induced aggregates were reversible in nature and were amenable to disaggregation in presence of LdCyP. In contrast, the naturally formed AdK aggregates
were irreversible and therefore could not be reactivated by LdCyP-chaperone. Detailed structural and biochemical analysis of the two forms of aggregates revealed marked differences in the morphology between two forms of aggregates. Disaggregating and reactivating properties of LdCyP remained intact even after truncating 88-amino acids from the N-terminal end of the full-length LdCyP. A further search for smaller LdCyP fragment has resulted in identification of one LdCyP-decapeptide that appeared to
have AdK stimulating activity. Although, the physiological significance of this phenomenon in L. donovani has not yet been firmly established, it is well known that like many other developmentally regulated parasitic proteins, AdK, along with adenosine deaminase (ADA), exhibits high specific activity during transformation from promastigote to amastigote. Hence, the importance of in vivo regulation of AdK activity, responsible for Ado uptake in purine auxotrophs, during multiplication of amastigote within the
macrophage of hosts cannot be overlooked. Furthermore, in view of previous observation, that in stressed leishmanial cells retrograde translocation of LdCyP from the endoplasmic reticulum to cytoplasm is accompanied with increased uptake of Ado, makes it relevant. Hence, development of peptide-based antagonist as a tool to control the AdK activity might be a possible strategy to inhibit in vivo parasite multiplication. Studies on the molecular mechanism of AdK aggregation and the mechanism
by which LdCyP exerts its unique chaperone function to reactivate the activity by disrupting only the
ADP-induced aggregates and a detailed structural characterization and conformational analysis of the
two forms of the aggregates is therefore clearly important.
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| Date |
2013
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| Type |
Thesis
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/2064/1/Thesis_Full_and_Final.pdf
Mukherjee, Debalina (2013) Adenosine Kinase Reactivation by Leishmania donovani Coded Cyclophilin and its Truncated Form. PhD thesis, Calcutta University. |
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| Relation |
http://www.eprints.iicb.res.in/2064/
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