5.1 The Z domain scaffoldThe work in this thesis is based on the immunotechnological use of affinity ligands(denoted affibodies) selected from protein libraries based on the so-called Z domain,utilized as scaffold for library constructions. This Z domain is a 58 aa non-cysteinprotein consisting of three anti-parallel α-helices forming a bundle structure. The Zdomain corresponds to an engineered variant of the native B domain ofstaphylococcal protein A, in which an Asn28-Gly29 dipeptide sequence, sensitive tofusion protein cleavage by hydroxylamine, has been changed into an Asn-Alasequence. In addition, an alanine residue at position one has been changed into avaline (Nilsson et al., 1987). This Z domain has been frequently used as affinityfusion partner for the production of either Z or ZZ-fusion proteins in a number ofdifferent host cells (
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