PRODUCTION OF SYNTHETIC SPIDER DRAGLINE SILK PROTEIN IN PICHIA-PASTORIS

The methylotrophic yeast Pichia pastoris was tested as a host for the production of long, repetitive protein polymers. Synthetic genes for a designed analog of a spider dragline silk protein were readily expres sed at high levels under control of the methanol-inducible AOX1 promot er. Transformants containing multiple gene copies produced elevated le vels of silk protein, but of a variety of altered sizes as a result of gene rearrangements at the time of transformation. Genes up to 3000 c odons in length or longer could be expressed with no evidence of the p revalent truncated synthesis observed for similar genes in Escherichia coli, though genes longer than 1600 codons were expressed less effici ently than shorter genes. Silk-producing P. pastoris strains were stab le without selection for at least 100 doublings.