Chicken ovalbumin contains an internal signal sequence

Ovalbumin is shown to contain an internal rather than an amino-terminal signal sequence. This internal signal can be recovered in a tryptic fragment which comprises residues 229--276 of mature ovalbumin and contains a region of striking sequence homology to amino-terminal cleaved signals of two other oviduct secretory proteins. The isolated tryptic fragment is used as a probe to demonstrate that a signal receptor is present in membrane vesicles derived from the rough but not in those derived from the smooth endoplasmic reticulum.