Calreticulin in the green alga Enteromorpha sp

ANDREA A. AMBROSIO; M. FERNANDA TRONCOSO; M. MERCEDES IGLESIAS; EDUARDO I. SÁNCHEZ; CARLOTA WOLFENSTEIN-TODEL

Portsmouth, Inglaterra

Congreso; 18th International Lectin Meeting, (INTERLEC 18); 1998

Calreticulin, is the major Ca2+-binding protein in the endoplasmic reticulum of eukaryotic cells. It has also been shown to be a molecular chaperone, because it is a lectin that recognizes specifically partially trimmed, monoglucosylated, N-linked conserved during evolution (Krause and Michalak, Cell 88, 439-443, 1997). In the last few years increasing attention has been directed toward its characterization in plant cells. However, its presence in algae had not yet been detected. In the present study we show that a calreticulin-like protein is expressed in the alga Enteromorpha sp. Using a method which involves various centrifugations and sodium deoxycholate and HgCl2 a fraction enriched in soluble endoplasmic reticulum proteins was obtained (Hassan et al., Biochem. Biophys. Res. Comm. 211, 54-59, 1995). Further purification was achieved by affinity chromatography on a mannan-agarose column. SDS-PAGE of the material obtained showed two major bands of 66 and 55 kDa apparent molecular masses, and some minor bands. These two bands stained blue with the cationic dye “Stains all”, characteristic of Ca2+-binding proteins. In addition, this protein doublet was recognized by polyclonal antibodies against human calreticulin, as shown by Western blot which is consistent with the fact that this protein is remarkably preserved in all eukaryotic cells.