Hi,

I was looking at the sequence of the pCR4 Blunt TOPO plasmid (https://www.snapgene.com/plasmids/topo_cloning_vectors/pCR4Blunt-TOPO_(linearized)) and I noticed that a 26 codon coding sequence prior to the TOPO cloning site (labelled as LacZa in the map on Addgene) is not actually from Beta Galactosidase. I ran a protein blast on the translation (MTMITPSSELTLTKGTSPAGLNEFAL) and it is a perfect match for RuBisCO (rbcS2) residues 1-26 from Limonium gibertii.

I wondered if anyone has noticed this before, and knows the purpose of this sequence in the vector.

Thanks,

Chris