Method for cloning Cloning of product proteins into the intein is generally done using the unique BsrG I site (TGTACA) at the end of the intein and one of several sites downstream from the product protein (typically Hind III). The critical detail to remember is that the intein peptide sequence must end with the amino acids: VVVHN, to be followed immediately by the initial residue of the product protein (usually methionine). To make this possible without adding any additional residues to the product protein, we created a translationally silent restriction site at the end of the intein (BsrG I). This site starts at nucleotide 7440 if the pET/ELP-I-CAT sequence we have sent. Note that the BsrG I site is not in frame with the intein. See below for a schematic of the actual upstream fusion joint:
