The Spectroscopic Properties Analysis Of Human Centrin 2

Centrins are rooting in EF-hand family (namely CaM superfamily) whose molecular weight are approximately 20kDa. They are conserved from yeast to human in the organism kingdom. Since the first discovery of this family member in the green alga Tetraselmis striata, the family is constantly growing larger and larger. These proteins are basically concentrated in the spindle pole body of yeast cells and centrosomes of higher eukaryotes, they are closely related to the nucleus and nuclear membrane material. In addition, some new functions are discovered recently, including the nucleus DNA repair process, mRNA transportation across the cell membrane and the voltage-gated Ca2+ channels in Paramecium.Human centrins have a common characteristics with other centrins. There are four isomers carried in the Homo sapiens namely centrin 1, centrin 2, centrin 3 and centrin 4, (abbreviated as HsCenl-HsCen4) having similar structures and different functions. Recent studies showing that the vertebrate centrin 3 participate in the process of cell division directly, centrin 4 were involved in some ciliated cell growth and differentiation, and the vertebrates centrin 1 and centrin 2 play important roles in the separation of two centrosomes. The centrosome abnormalities are closely related with human diseases in higher eukaryotes because of centrins are indispensable in the process of centrosome duplication.This paper made the the Human centrin 2 (HsCen2) as a research object based on the studies of Euplotes Octocarinatus centrin (EoCen), studying related properties of the protein as the followings.First of all, the preliminary studies of the spectrals for HsCen2 combined with metal ions were made. The resonance light scattering (RLS) experiments showed that the aggregation generated when HsCen2 interact with metal ions and one protein molecule could combine two Tb3+, Lu3+, La3+ and two equivalent Ca2+. The fluorescence lifetime decreased when HsCen2 exposured to the atmosphere of the metal ions and the lifetime values were no longer changed when HsCen2 have combined two equivalent meltal ions. In addition, the average constant (KTb-HsCen2:=3.89×1012) for HsCen2 and Tb3+ was obtained in the reaction system in which HBED competed with HsCen2 for Tb3+.Secondly, the factors which could effect the aggregation of HsCen2 were explored, including the protein concentration, the temperature, ionic strength and the type of metal ions. The results demonstrated that the greater the concentration of the protein, the more aggregation generated; high temperature could promote HsCen2 assemble; increasing the ionic strength could inhibit HsCen2 gathering; the degree of HsCen2 aggregation was increased after reaction with different metal ions (La3+, Eu3+, Tb3+ and Lu3+) along with the ionic radius decreased.Finally, we made a preliminary comparision on the reaction for HsCen2 and EoCen with metal ions which told us that HsCen2 was more sensitive to the low concentration of Ca2+ than EoCen, the EoCen aggregation degree was far outweigh than HsCen2 under the same condition, the fluorescence lifetime of HsCen2 and EoCen would decrease because the comformation were changed and the hydrophobic surfaces were exposed after combing with metal ions.