ABSTRACT
Certain structural features of secreted proteins may function as "sorting signals" to direct the various steps required in the secretory pathway. In order to identify and study the function of these signals we have cloned a complete cDNA gene encoding rat serum albumin (RSA) and expressed this gene in COS-1 cells via an SV40-plasmid shuttle vector. The gene was constructed by splicing together a segment of genomic DNA and three cDNA fragments excised from recombinant plasmids. DNA endonuclease digestion and ligation at restriction sites common to overlapping regions of these four RSA DNA fragments assured the maintenance of the translation reading frame during the construction of this gene. COS-1 cells transfected with the recombinant vector containing the full-length RSA gene (pSV2rsa) synthesize and secrete RSA immunoreactive material into the culture medium. This mammalian expression system provides a means to study the signals and processes involved in intracellular transport of secreted proteins.
