Abstract
A high molecular mass (approx. 600 kDa), vesicle-associated protein (VAP-1) has been identified in the eggs of the sea urchin S. purpuratus. Characterization of this protein reveals that it is peripherally associated with a population of acidic vesicles in the egg. Additionally, VAP-1 is phosphorylated on serine and/or threonine residues and it is sensitive to calcium-dependent proteolytic modification. Partial cDNA sequence analysis suggests that VAP-1 may function as an RNA-binding protein. The potential functions of VAP-1 during early sea urchin development are discussed, including possible roles as a cytoplasmic RNA-binding protein involved in mRNA localization or as a nuclear protein precursor that will be translocated to specific nuclei later in development to function in RNA processing or splicing.