PROTEOLYTIC PROCESSING OF THE DROSOPHILA SPATZLE PROTEIN BY EASTER GENERATES A DIMERIC NGF-LIKE MOLECULE WITH VENTRALISING ACTIVITY

Biochemical interactions underlying the generation of the ventralising signal during Drosophila embryogenesis were investigated by the expre ssion of recombinant Easter and Spatzle proteins. An active form of Ea ster protease cleaves the Spatzle protein, generating a carboxytermina l polypeptide fragment which, when microinjected into the perivitellin e space of a spatzle deficient embryo, directs production of ventrolat eral pattern elements. This Spatzle carboxyterminal fragment is a disu lfide-linked dimer and modelling suggests that the core disulfide bond s and dimer arrangement of this fragment are highly similar to vertebr ate nerve growth factor. Thus Spatzle is a member of a new family of n eurotrophin-like signalling molecules in invertebrate development. (C) 1998 Elsevier Science Ireland Ltd.