Hexa-histidine

E. coli strain BL21(DE3) (F ompT ksdSafra ms ) gal dcm) (Novagen, Madison, WI, USA) was used as a host for recombinant OPH expression. Recombinant plasmids pTOH and pEOH that contain OPH gene fused with hexa-histidine affinity tag under trc and T7 promoter, respectively, as control vectors and pTTOH and pETOH that contain OPH gene fused with Tat signal sequence and hexa-histidine affinity tag under trc and T7 promoter, respectively, were used (Fig. 1). 

Fig.l. Gene maps of recombinant plasmids pTOH, pTTOH, pEOH, and pETOH. Abbreviations Pnc, trc promoter Px7, T7 and lac hybrid promoter Tat, twin-arginme TorA signal sequence of TMAO reductase OPH, organophosphoms hydrolase gene Hisg, hexa-histidine affinity tag. 

Metal affinity columns can be used for the purification of antibodies with a hexa-Histidine tag. Immobilized metal affinity chromatography is incompatible, in our own experience, with direct loading of antibodies in supernatants... 

Key Words Ligation-independent cloning T7 expression system pET vector hexa-histidine tag. 

PIMENTEL, G.J., et al., Hexa histidine tag as a novel alternative for one step direct labelling of a single chain Ev antibody fragment with Tc, Nucl. Med. Commun. 22 (2001) 1089-1094. 

On the other hand, recombinant FucA from E. coli expressed as a fusion protein with a hexa-histidine tag has been immobilized by using metal-chelate supports (Ardao et al. 2006). IMAC supports allowed FucA purification and immobilization in one step in order to obtain an immobilized FucA catalyst for aldol... 

His tag. The ability of the imidazole moiety of the histidine residue to bind divalent metal ions such as nickel, iron, and cobalt can be used to purify histidine-containing proteins on a column which has such divalent metals bound to it. To streamline the purification procedure of any desired protein, such histidines are deliberately added to a protein of choice by cloning a four- to sixfold CAG repeat sequence into the expression construct upstream of the gene of interest so as to express an N-terminal or C-terminal tetra- or hexa-His tag. From experience, especially in E. coli, C-terminal tagging often yields superior results to N-termi-... 

---