Could be involved in the differentiation of ectodermal lineages and subsequent patterning of the embryo. Binds 1 zinc ion per subunit. First detected in a perinuclear region, then in an apical and submembranous position just before its secretion into the perivitelline space. Embryonic. The protein is first detected in early blastula stages, its level peaks in late cleavage, declines abruptly before ingression of primary mesenchyme cells and remains constant in late development.