A UNIVERSAL TAG FOR RECOMBINANT PROTEINS

Incorporation of tags into recombinant proteins can facilitate their i dentification and purification, In addition, these tags can also be us ed to monitor the trafficking or localization of the recombinant prote ins inside the cells. Several such tags have been developed. However, the lengths of these tags make it cumbersome to incorporate them into the desired proteins. Typically, one must subclone the desired cDNA in to a plasmid containing the tag sequence at a suitable restriction sit e or ligate a synthetic oligonucleotide containing the tag sequence at a suitable restriction site in the cDNA of the desired protein. These manipulations can be avoided, if one uses a short peptide tag that ca n be incorporated by PCR. We show here that a short peptide tag, RYIRS , can be easily incorporated at the C termini of recombinant proteins by PCR. We also showed that by using a mAb specific for this peptide s equence, the tagged proteins could be easily detected in Western blot analysis, immunofluorescence staining, and immunoprecipitation. The in teractions between this tag sequence and the mAb have been well charac terized. One can take advantage of this information and control the re activities between the tagged proteins and the mAb by varying the leng ths of the peptide tags. Furthermore, we showed that this tag can be u sed to monitor whether a recombinant protein is properly translated an d terminated because the interactions between this tag sequence and th e mAb requires that the tag be at the C-terminus of the protein. (C) 1 996 Academic Press, Inc.