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About the Authors:
Deepshikha Verma
Contributed equally to this work with: Deepshikha Verma, Aruna Murmu
Affiliations Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India, Tata Institute of Fundamental Research, Center for Interdisciplinary Sciences, Hyderabad, India
Aruna Murmu
Contributed equally to this work with: Deepshikha Verma, Aruna Murmu
Affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
ORCID http://orcid.org/0000-0002-0112-0026
Samudrala Gourinath
Affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
Alok Bhattacharya
Affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
Kandala V. R. Chary
* E-mail: [email protected]
Affiliations Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India, Tata Institute of Fundamental Research, Center for Interdisciplinary Sciences, Hyderabad, India
ORCID http://orcid.org/0000-0003-1189-8867Abstract
Cell cycle of Entamoeba histolytica, the etiological agent of amoebiasis, follows a novel pathway, which includes nuclear division without the nuclear membrane disassembly. We report a nuclear localized Ca2+-binding protein from E. histolytica (abbreviated hereafter as EhCaBP6), which is associated with microtubules. We determined the 3D solution NMR structure of EhCaBP6, and identified one unusual, one canonical and two non-canonical cryptic EF-hand motifs. The cryptic EF-II and EF-IV pair with the Ca2+-binding EF-I and EF-III, respectively, to form a two-domain structure similar to Calmodulin and Centrin proteins. Downregulation of EhCaBP6 affects cell proliferation by causing delays in transition from G1 to S phase, and inhibition of DNA synthesis and cytokinesis. We also demonstrate that EhCaBP6 modulates microtubule dynamics by increasing the rate of tubulin polymerization. Our results, including structural inferences, suggest that EhCaBP6 is an unusual CaBP involved in regulating cell proliferation in E. histolytica similar to nuclear Calmodulin.
Author summary
E. histolytica, the etiological agent of amoebiasis, is a protozoan parasite responsible for around 100,000 deaths per year in developing nations. Though the organism has been identified more than 100 years back, there is not much understanding about the biology of this organism. Calcium signaling plays an important role in the biology of this organism. Here we show structure-functional relationship of one of the Ca2+-binding proteins (abbreviated as EhCaBP6) and suggest its involvement in cell division in this parasite. EhCaBP6, a nucleo-cytosolic Ca2+-binding protein, is a microtubule end binding protein and overexpression of its gene induces an increase in number of microtubular assemblies...