pTYB12 is an E. coli cloning and expression vector (7417 bp) used in the IMPACT? Protein Purification System which allows the overexpression of a target protein as a fusion to a self-cleavable affinity tag (1,2). It is a N-terminal fusion vector designed for in-frame insertion of a target gene into the polylinker, downstream of the intein tag (the Sce VMA intein/chitin domain, 55 kDa)(3,4). This allows the N-terminus of the target protein to be fused to the intein tag. The self-cleavage activity of the intein allows the release of the target protein from the chitin-bound intein tag, resulting in a single column purification of the target protein. This vector can be used in conjuction with pTYB2 (NEB #N6702S) to test which fusion construction (N-terminal or C-terminal) maximizes the expression and yield of a target protein.