Structural studies of the scrapie prion protein using mass spectrometry and amino acid sequencing

• Published in: Biochemistry (Easton) Vol. 32; no. 8; pp. 1991 - 2002
• Main Authors: Stahl, Neil, Baldwin, Michael A, Teplow, David B, Hood, Leroy, Gibson, Bradford W, Burlingame, Alma L, Prusiner, Stanley B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.03.1993
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Brain - microbiology; Chromatography, Gel; Chromatography, High Pressure Liquid; Cricetinae; Fundamental and applied biological sciences. Psychology; Mass Spectrometry - methods; Mesocricetus; Miscellaneous; Molecular Sequence Data; Peptide Fragments - isolation & purification; Prions - chemistry; Prions - genetics; Protein Processing, Post-Translational; Proteins; Infection; Virus; Posttranslational modification; Proteins; Scrapie; Viral disease; Edman degradation; Prion; Mass spectrometry; Aminoacid sequence; Scrapie agent
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00059a016

The only component of the infectious scrapie prion identified to date is a protein designated PrPSc. A posttranslational process converts the cellular PrP isoform (PrPC) into PrPSc. Denatured PrPSc was digested with endoproteases, and the resulting fragments were isolated by HPLC. By both mass spectrometry and Edman sequencing, the primary structure of PrPSc was found to be the same as that deduced from the PrP gene sequence, arguing that neither RNA editing nor protein splicing feature in the synthesis of PrPSc. Mass spectrometry also was used to search for posttranslational chemical modifications other than the glycosylinositol phospholipid anchor attached to the C-terminus and two Asn-linked oligosaccharides already known to occur on both PrPSc and PrPC. These results contend that PrPSc molecules do not differ from PrPC at the level of an amino acid substitution or a posttranslational chemical modification; however, we cannot eliminate the possibility that a small fraction of PrPSc is modified by an as yet unidentified posttranslational process or that PrPC carries a modification that is removed in the formation of PrPSc. It seems likely that PrPSc differs from PrPC in its secondary and tertiary structure, but the possibility of a tightly bound, disease-specific molecule which purifies with PrPSc must also be considered.