Constructs were transformed into DH5α cells, cloned, and sequenced (ABI Prism 3100Avant, Applied Biosystems) . Validated constructs of interest were transformed into an Escherichia coli production cell line, BL21(DE3), containing the pACYC184 expression plasmid (Avidity, Denver, USA) containing an isopropylβ-d-1-thiogalactopyranoside (IPTG)-inducible BirA gene to express biotin-ligase. This leads to almost complete in vivo biotinylation of the desired product (Leisner et al. 2008 ).