Expression of the Arabidopsis thaliana AtJ2 Cochaperone Protein in Pichia pastoris

A vector was constructed for intracellular expression of the Arabidopsis thaliana DnaJ homologue AtJ2 in the methylotrophic yeast Pichia pastoris. The vector includes DNA encoding an amino-terminal histidine-tag, to simplify protein purification. Shake-flask cultures could be induced to produce approximately 250 mg/ L of AtJ2. Purified recombinant AtJ2 was able to stimulate the ATPase activities of both the Escherichia coli and Zea mays cytoplasmic Stress70 chaperone proteins five- to ninefold. The carboxy terminus of AtJ2 is –CAQQ, a protein farnesylation motif. When transformed P. pastoris was induced to synthesize AtJ2 in the presence of [3H]mevalonolactone, radioactivity was incorporated into the protein, suggesting farnesylation.