UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2004 Meeting


Section: Electricity and Biophysics


Title:
Thermodynamic studies of human centrins and calmodulin interaction with target proteins


Authors:
Claudia Firanescu, Aurel Popescu


Affiliation:
Department of Electricity and Biophysics, Faculty of Physics, University of Bucharest


E-mail


Keywords:


Abstract:
The aim of this work was to characterize the thermodynamic parameters describing the interactions of calcium proteins with target peptides. Our interest was focused on calmodulin (CaM) and three of the four human centrin isoforms (HsCen1 to HsCen3) in interaction with their specific targets. CaM, belonging to the EF-hand family, is involved in the calcium signalling processes in the cells. CaM can bind four Ca2+ with affinity constants, of the order 105 – 106 M-1. One of the characteristic properties of CaM is its capacity to bind and control a large number of molecules involved in distinct biological processes. Centrins are calcium proteins found in association with the centrosomes in animal cells, and spindle pole bodies in yeast. Alike CaM, the centrins consist of two structural domains, each containing two putative Ca2+-binding EF-hand motifs. It was recently demonstrated that the capacity of HsCen2 to bind amphiphilic peptides is primarily mediated by its C-terminal domain. The complexes between these proteins and their specific ligands still need additional conformation studies and a more detailed functional characterization. It is expected that their specificity for target binding and their Ca2+-dependence structure may be different for CaM and centrins. In order to answer these questions, we studied the thermodynamic fingerprints of interaction between calcium proteins and the mentioned peptides. ITC experiments allowed the determination of the thermodynamic parameters of the interactions between the EF-hand proteins and the targets peptides, the binding constants and the stoichiometry. This study has made possible the comparison of the interaction mechanisms for the proteins from the same class, and also the appreciation of the ion dependence of their interaction (Ca2+ in this case).