IDENTIFICATION AND CHARACTERIZATION OF A CONSTITUTIVE HSP75 IN SEA-URCHIN EMBRYOS

An antiserum against a hsp of the 70-kDa family was prepared, by means of a fusion protein, which was able to detect a constitutive 75-kDa h sc in the sea urchin P. lividus. This hsc was present both during ooge nesis and at all developmental stages. A two-dimensional electrophores is has revealed four isolectric forms of this 75-kDa hsc. The amino ac id sequence of the fragment used to prepare the anti-hsp70 antibodies revealed a 43% identity with the corresponding part of sea urchin sper m receptor, and in mature eggs a brighter immunofluorescence was seen all around the cell cortex where the receptor for sea urchin sperm is localized. In oocytes the hsp75 was localized in the cytoplasms but no t in the nuclei. In the embryos a higher hsp75 concentration was found in the portion facing the lumen of the cells which invaginate at gast rulation. (C) 1997 Academic Press.