Molecular cloning of a candidate chicken prion protein.

Fractions enriched for acetylcholine receptor-inducing activity from chicken brain were found to contain a protein that was approximately 30% homologous with mammalian prion proteins [Harris, D. A., Falls, D. L., Johnson, F. A. & Fischbach, G. D. (1991) Proc. Natl. Acad. Sci. USA 88, 7664-7668]. To extend these observations, we recovered genomic clones encoding a putative chicken prion protein (PrP). Like mammalian PrP molecules, the candidate chicken PrP is encoded by a single-copy gene and the entire open reading frame is found within a single exon. All of the structural features of mammalian PrP were found in the chicken protein. When the N-terminal repeats of PrP were not considered, the chicken and mammalian proteins were approximately 55% homologous, allowing for conservative substitutions. Screening of a chicken genomic DNA library failed to identify a more closely related chicken PrP homologue. These findings argue that the protein which purifies with acetylcholine receptor-inducing activity is chicken PrP.