CHARACTERIZATION OF CENTRIN FROM SCHISTOSOMA MANSONI: CALCIUM BINDING PROPERTIES AND POLYMERIZATION DYNAMICS

CHARACTERIZATION OF CENTRIN FROM SCHISTOSOMA MANSONI: 
CALCIUM BINDING PROPERTIES AND POLYMERIZATION DYNAMICS
Almerita Guimarães Lopes, Bruna de S. M. Martins, Thais Rangel Figueiredo and 
Ana Eliza Zeraik.
Centro de Biociências e Biotecnologia – UENF Laboratório de Química e Função de 
Proteínas e Peptídeos, LQFPP – UENF, Rio de Janeiro – RJ
*email: [email protected]

The Schistosoma mansoni parasite is the main cause of schistosomiasis on the 
American continent. Currently the disease is treated with the only medication 
available, Praziquantel, which acts by destabilizing Ca2+ homeostasis in adult worms. 
Calcium acts in signaling pathways that controls gene expression, muscle 
contraction, among others. Thus, calcium-binding proteins are potential new targets 
against this parasite.
Centrins are calcium-binding proteins located in centrioles, fundamental in centriole 
replication and cytoskeleton composition. The ability to form multimers and filaments 
at different levels has been reported in several species. Centrins from yeast, algae 
and humans (HsCentrin 1, 2 and 3) present this capacity in the presence of calcium. 
S. mansoni has one centrin, SmCentrin, which has 64% sequence identity with 
HsCentrin 3, and 51% with HsCentrin 2 and HsCentrin1, but it is not known whether 
SmCentrin is capable of oligomerize and the factors that influence this process.
In this project, we focused on the biophysical characterization of recombinant 
SmCentrin and the factors that might influence its polymerization.
SmCentrin was cloned in pET28a and expressed in E.coli Rosetta (DE3) strain. The 
protein was purified by Ni-NTA affinity chromatography followed by Size exclusion 
chromatography on a Superdex 75 column.After these processes, the samples were 
analyzed on polyacrylamide gel (SDS-PAGE), which indicated that the protein was 
obtained with a high degree of purity. SmCentrin was able to bind Ca2+, as assessed 
by Isothermal Titration Calorimetry. Circular dichroism experiments showed a α-
helical rich protein and the presence of calcium did not influence its secondary 
structure. However, fluorescence experiments with the ANS probe indicated tertiary
structure alterations in the presence of calcium. Cross-linking experiments indicated 
that the protein concentration is a critical factor in its polymerization. 
Other experiments will be carried out to investigate the factors that influence the 
polymerization of SmCentrin by measuring particle size, in addition to evaluating the 
protein structure and its stability.
This work was supported by Conselho Nac. Des. Cient. Tecnologico CNPq