CHARACTERIZATION OF CENTRIN GENES IN PARAMECIUM

Centrins are highly conserved, ubiquitous cytoskeletal components whic h belong to the EF-hand superfamily of Ca2+-modulated proteins. We rep ort here the molecular characterization of new members of the centrin family, Paramecium centrins. Previous studies described the organizati on of the infraciliary lattice (ICL), the innermost cortical cytoskele tal network of Paramecium, and showed that it was composed of a set of low-molecular-mass, Ca2+-binding polypeptides [Garreau de Loubresse, N., Klotz, C., Vigues, B., Rutin, J. & Beisson, J. (1991) Biol. Cell 7 1, 217-225]. In this paper we show that these polypeptides are recogni zed by specific anti-centrin polyclonal antibodies. Their microsequenc es revealed four distinct N-termini. For one of them, ICL1, N-terminal and internal peptide sequences were used for PCR amplification and cl oning of a DNA fragment containing a complete centrin coding sequence. The deduced amino acid sequence presents about 50% identity with thos e of centrins from other species. Further molecular analysis allowed u s to identify two additional closely related, co-expressed ICL1 genes, providing the first example of a centrin multigenic family in a micro organism.