Bovine β-lactoglobulin A was expressed in Escherichia coli in its mature form. The gene was constructed using a cDNA clone which coded for amino acid residues Leu-11 to He-162 and a synthetic oligonucleotide coding for the initial 10 amino acids preceded by a translational start. The met-β-lactoglobulin was expressed using a tac promoter vector, pTTQ18, and accounted for approximately 15% of the total cellular protein. The recombinant met-β-lactoglobulin migrated with the same molecular weight as native β-actoglobulin A on SDS-PAGE. The majority of the met-β-lactoglobulin produced was found in an insoluble form but could be solubilized using guanidine-HCI. The renatured preparation was > 80 % pure and migrated similarly to purified β-lactoglobulin A under nondenaturing conditions.

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