Y3-galactosidase

Pairs of plasmids encoding LexA and B42 fusion proteins were transformed into the yeast strain L40, in which the dimerization of LexA and B42 fusion proteins leads to transcription of the reporter genes HIS3 and lacZ. Growing these yeast strains in the presence of BGMtx then complemented the histidine auxotrophy of the yeast and also induced the expression of y3-galactosidase. These experiments clearly showed that BG derivatives can be used as CIDs to control transcription in yeast and, more generally, also demonstrated how AGT fusion proteins can be used to control protein dimerization in vivo. 

The enzyme y3-galactosidase was purifled directly from crude cell extracts using expanded bed chromatography on another second generation matrix, Ni + loaded streamline chelating resin. The natural histidine content of the enzyme permitted the enzjune to be recovered in almost 90% jdeld and 5.95-fold purification from a crude unclarified cell extract (67). 

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