Reversal of ADP-Mediated Aggregation of Adenosine Kinase by Cyclophilin Leads to Its Reactivation
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
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| Title |
Reversal of ADP-Mediated Aggregation of Adenosine Kinase by Cyclophilin Leads to Its Reactivation
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| Creator |
Sen, Banibrata
Chakraborty, Anutosh Datta, Rupak Bhattacharyya, Debasish Datta, Alok K |
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| Subject |
Infectious Diseases and Immunology
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| Description |
Cyclophilins have been implicated in several important cellular functions. Our earlier results showed that reactivation of adenosine kinase (AdK) by CyP (LdCyP) from the parasitic protozoa Leishmania donoVani is accompanied with disaggregation of the enzyme [Chakraborty, A., et al. (2002) J. Biol. Chem. 277, 47451-47460; Chakraborty, A., et al. (2004) Biochemistry 43, 11862-11872]. However, it remained to be known why the enzyme displayed progressive inhibition during the time-dependent reaction and
what LdCyP does to prevent and/or reverse the inhibition. Herein, we demonstrate that one of its reaction
products, ADP but not AMP, facilitates the formation of AdK aggregates, leading to its inactivation.
Further studies revealed that LdCyP reactivates the enzyme by withdrawing the ADP inhibition. To
investigate the molecular mechanism, the intrinsic tryptophan fluorescence and polarization of AdK were
monitored in the presence of either LdCyP or ADP and in combination thereof. Whereas in the presence
of LdCyP the tryptophan fluorescence emission maxima of AdK exhibited a red shift, ADP had a quenching
effect. However, both the red shift and quenching became less noticeable when one (W234) of the two
tryptophan residues of AdK was altered, indicating W234 fluorescence is relatively more sensitive to
both LdCyP and ADP binding. Kinetic measurements indicated that LdCyP-facilitated reactivation of
AdK is accompanied with a concomitant increase in the KD of ADP but not of AMP. Interestingly, addition
of myokinase (MK) and pyruvate kinase (PK) along with phosphoenolpyruvate, either singly or in
conjunction, to the AdK reaction mixture led to its reactivation. The effect of PK but not of MK could
be substituted by CyP and vice versa. Taken together, the results suggest that LdCyP-induced reactivation
occurs due to conformational reorientation of AdK in a manner that decreases the affinity of the enzyme
for ADP with consequent relief from the ADP-mediated aggregation.
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| Date |
2006
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/419/1/BIOCHEMISTRY%2C_45(_1)%2C__263%2D271[142].pdf
Sen, Banibrata and Chakraborty, Anutosh and Datta, Rupak and Bhattacharyya, Debasish and Datta, Alok K (2006) Reversal of ADP-Mediated Aggregation of Adenosine Kinase by Cyclophilin Leads to Its Reactivation. Biochemistry, 45 (1). pp. 263-271. |
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| Relation |
htpp://dx.doi.org/10.1021/bi0518489
http://www.eprints.iicb.res.in/419/ |
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