Part:BBa_K5398002

This part is a part of the circular mRNA (cmRNA) (3´ side). To generate the squid ring proteins with various long tandem repeats (TRn), we utilized the td intron, an intron of the td gene from T4 phage belonging to group IE, which circularizes the exon to form a back-splice junction (BSJ) in a reaction catalyzed by guanosine. To ensure that the ribosomes do not translate the ORF of TRn from unprocessed linear mRNA, the ribosome binding sequence (RBS) and translation initiation codon ATG were placed downstream of the TRn coding sequence. Consequently, the regulatory sequences were located upstream of the coding sequence only after circularization of the mRNA. To purify the resulting TRn polypeptides, a His tag was incorporated into the ORF. If the mRNA is circularized, the ribosome could circle the cmRNA, producing a long repeating polypeptide.