The pore-forming and cytoplasmic domains of the neurogenic gene product, BIG BRAIN, are conserved between Drosophila virilis and Drosophila melanogaster

The Drosophila BIG BRAIN (BIB) protein functions critically in the determination of neuroblasts in the embryonic ectoderm and many other cell types. BIB is a member of the MIP family of transmembrane channel proteins. The conserved channel domain of BIB is flanked by amino- and carboxy-terminal cytoplasmic domains of unique sequence, which comprise over two-thirds of the protein. To determine whether the cytoplasmic domains of BIB are important for BIB function, we have cloned and sequenced the bib gene of D. virilis and compared it with that of D. melanogaster. Here we report that the channel domain and both cytoplasmic domains are highly conserved between the two species. The conservation of the cytoplasmic domains indicates that they are critical to BIB function. bib transcripts are found in similar patterns in both species, indicating that the developmental function(s) of BIB have also been conserved. (C) 1997 Elsevier Science B.V.