Solvent-dependent precipitation of prion protein.
The misfolded isoform of the prion protein (PrP(Sc)) possesses many unusual physiochemical properties. Previously, we and others reported on the differential partitioning of PrP(Sc) from plasma derived therapeutic proteins during their purification processes. To understand the driving force behind these partitioning differences, we investigated the effects of various solvent conditions on the precipitation of PrP(Sc). In a physiological buffer, PrP(Sc) remained in the supernatant after low speed centrifugation. At pH 5, PrP(Sc) precipitation was nearly complete regardless of the salt content. PrP(Sc) could also be precipitated at pH 8 by adding ethanol, but this precipitation was salt dependent. Based on these observations, an empirical mathematical model was constructed in which the PrP(Sc) precipitation trends were fully described as a function of solvent pH, salt, and ethanol concentration. This model consistently predicted PrP(Sc) partitioning during cold ethanol precipitation steps used in plasma protein purification processes, as shown by experimentally determined distributions of PrP(Sc) and transmissible spongiform encephalopathy (TSE) infectivity. These results indicate that pH, salt, and ethanol content are the major solvent factors determining the precipitation of the infectious PrP(Sc) in these processes and may provide a useful tool for assessing the differential partitioning of PrP(Sc) in a given solvent environment.
Cai
Kang
K
Department of Pathogen Safety and Research/Biological Products, Bayer Corporation, 85 T.W. Alexander Dr., Research Triangle Park, NC 27709, USA. kang.cai.b@bayer.com
Miller
Jeanette L C
JL
Stenland
Christopher J
CJ
Gilligan
Kevin J
KJ
Hartwell
Randal C
RC
Terry
Jarrett C
JC
Evans-Storms
Rosemary B
RB
Rubenstein
Richard
R
Petteway
Stephen R
SR
Lee
Douglas C
DC
D000465:Algorithms; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry*; D011232:Chemical Precipitation; D006224:Cricetinae; D000431:Ethanol; D006863:Hydrogen-Ion Concentration; D018620:PrPSc Proteins / Q000737:chemistry*; D011328:Prions / Q000737:chemistry / Q000302:isolation & purification*; D012965:Sodium Chloride; D012997:Solvents
D001798:Blood Proteins; D018620:PrPSc Proteins; D011328:Prions; D012997:Solvents; D000431:Ethanol; D012965:Sodium Chloride