Structural features of B family chorion sequences in the silkmoth Bombyx mori, and their evolutionary implications.

Partial protein sequences, and DNA sequences of corresponding cDNA and genomic clones were obtained and analyzed to reveal the primary structural features of major, developmentally middle or late components of the B chorion multigene family in Bombyx mori. Comparisons with other types of sequences confirm and clarify the tripartite domain structure of chorion proteins. Glycine-, leucine- and tyrosine-containing, tandemly repetitive peptides form the bulk of the amino-terminal and carboxy-terminal domains ('arms'). Extensive sequence homologies suggest a common evolutionary origin for the amino-terminal arms of some B. mori B sequences and the corresponding portions of members of a different (A) chorion multigene family in Antheraea polyphemus, a distantly related silkmoth.