Journal of Cell Science & Therapy
Open Access
ISSN: 2157-7013
+44 1300 500008
ISSN: 2157-7013
+44 1300 500008
Krylova VV, Andreev IM, Zartdinova RF and Izmailov SF
Accepted Abstracts: J Cell Sci Ther
Ca 2+ -pumping ATPase earlier identifi ed by us in the symbiosome membrane (SM) of broad bean root nodules was functionally characterized by following its catalytic and transport activities. In the experiments with Ca probes arsenazo III and chlorotetracycline, the initial Ca 2+ pumping rate was shown to achieve optimum at pH 7.2 and to signifi cantly and only slightly decline in the vesicles SM and symbiosomes, respectively, at extreme chosen pH values, 6.0 and 8. 0. It was established that the Ca 2+ -ATPase is capable of utilizing not only ATP for fueling the Ca 2+ transport through the SM but also other nucleotide triphosphates but with less effi ciency, with its affi nity for MgATP (K 0.5 for MgATP) is ~ 0.1 mM. In the reaction medium without added calcium, the rate of the Ca 2+ -pumping was found to be markedly stimulated by exogenous calmodulin, a well-known intracellular Ca 2+ -sensor. Based on the characteristics of Ca 2+ -dependent ATP/ITP-hydrolysis by symbiosomes using the Ca-EGTA buff er system, an affi nity of the Ca 2+ -ATPase for Ca 2+ (K 0.5 for free Ca 2+ ) was shown to be ~ 0.1 μM. In addition, it was found that the rate of Ca 2+ -dependent ITP hydrolysis by symbiosomes in the presence of KCl in the reaction medium was signifi cantly inhibited by nigericin indicating sensitivity of this process to symbiosome interior alkalinization. Th is fi nding and also revealed earlier insensitivity of the Ca 2+ -ATPase to SM electric polarization are consistent with the proposal that this enzyme uses H + as a counterion to facilitate transmembrane calcium translocation. Taken together, these results allow us to refer the SM Ca 2+ -pump to IIB type Ca 2+ -ATPases family
Krylova V.V. is senior science worker of Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow. She made her Ph.D. at the problem Ca 2+ transport across peribacteroid memdrane of broad bean and lupine root nodules. She is author of more than 40 publications, 16 from these in reputed journals.