An unconventional form of actin in protozoan hemoflagellate, Leishmania

Kapoor, Prabodh ; Sahasrabuddhe, Amogh A. ; Kumar, Ashutosh ; Mitra, Kalyan ; Siddiqi, Mohammad Imran ; Gupta, Chhitar M. (2008) An unconventional form of actin in protozoan hemoflagellate, Leishmania Journal of Biological Chemistry, 283 (33). pp. 22760-22773. ISSN 0021-9258

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Leishmania actin was cloned, overexpressed in baculovirusinsect cell system, and purified to homogeneity. The purified protein polymerized optimally in the presence of Mg2+ and ATP, but differed from conventional actins in its following properties: (i) it did not polymerize in the presence of Mg2+ alone, (ii) it polymerized in a restricted range of pH 7.0-8.5, (iii) its critical concentration for polymerization was found to be 3-4-fold lower than of muscle actin, (iv) it predominantly formed bundles rather than single filaments at pH 8.0, (v) it displayed considerably higher ATPase activity during polymerization, (vi) it did not inhibit DNase-I activity, and (vii) it did not bind the F-actin-binding toxin phalloidin or the actin polymerization disrupting agent Latrunculin B. Computational and molecular modeling studies revealed that the observed unconventional behavior of Leishmania actin is related to the diverged amino acid stretches in its sequence, which may lead to changes in the overall charge distribution on its solvent-exposed surface, ATP binding cleft, Mg2+ binding sites, and the hydrophobic loop that is involved in monomer-monomer interactions. Phylogenetically, it is related to ciliate actins, but to the best of our knowledge, no other actin with such unconventional properties has been reported to date. It is therefore suggested that actin in Leishmania may serve as a novel target for design of new antileishmanial drugs.

Item Type:Article
Source:Copyright of this article belongs to American Society for Biochemistry and Molecular Biology.
ID Code:15952
Deposited On:16 Nov 2010 13:40
Last Modified:17 May 2016 00:47

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