CLONING AND CHARACTERIZATION OF HLC-32, A 32-KDA PROTEIN-COMPONENT OF THE SEA-URCHIN EXTRAEMBRYONIC MATRIX, THE HYALINE LAYER

A 32-kDa protein (HLC-32) was purified from sea urchin embryos and characterized. In indirect immunofluorescence analysis this species was found to be distributed throughout the cytoplasm of the unfertilized egg but within 1 hr following fertilization was localized to the hyaline layer with some residual immunofluorescence remaining within the cytoplasm of the single cell embryo. By the early blastula stage the antigen was also detected in the basal lamina, indicating a bidirectional transport mode for this protein. A cDNA clone was isolated from a lambda Zap expression library. Sequence analysis revealed a protein rich in acidic (12.4 mole%) and basic (14.3 mole%) residues. Comparative sequence analysis revealed 41 and 47% amino acid sequence homology with two butanol-extractable proteins previously isolated from blastula stage embryos of the sea urchin Paracentrotus lividus. DNA gel blot analysis indicated that the gene encoding HLC-32 belonged to a small multigenic family, while in RNA gel blot analyses a 1.4-kB transcript was detected in ovaries but not gut, testes, mature eggs, or various stage embryos. At the early blastula stage of development this protein underwent a post-translational modification reaction which resulted in the loss of a 4-amino-acid peptide fragment from the amino-terminal end of this species. (C) 1994 Academic Press, Inc.