Schematic construction of the ankyrin repeat library using the pHDiEx acceptor vector. (A), The mono-ankyrin microgenes were polymerized by insertion/ligation to pHDiEx double digested by Bsm BI and Kpn I. The construction was subsequently digested by Bsp MI and recircularised by intramolecular ligation. This resulted in the substitution of the region containing the Rep cloning sites by the ankyrin repeats. The number of repeats differed from one clone to another, and usually ranged from 2 to 6 repeats. (B), Detailed sequences of the different DNA regions. Abbreviations: T7p, T7 promoter; pLac/RBS, lactose promoter and Ribosome binding site; DsbA ss, DsbA signal sequence; St2, Strep-Tag2 tag; H6, hexa-histidine tag.