PrPfr

PrPfr is an informal term used in prion research to denote a fragment of the prion protein (PrP). It is not a standardized designation with a single, universal meaning; the exact definition of PrPfr can vary among studies. In many contexts, PrPfr refers to a protease-resistant core fragment that is generated from PrP by limited proteolysis and used to investigate processing, conversion, or aggregation of PrP.

Generation and properties: The fragment is typically produced by proteolytic treatment (for example with proteinase K) that removes flexible portions of PrP and leaves a stable core. Because PrPfr is defined by proteolysis rather than sequence, its boundaries and composition can differ depending on the experimental conditions and antibodies used for detection. In some reports the term overlaps with well-characterized fragments such as the PrP27-30 fragment, but this is not universal.

Role in research: PrPfr fragments are used to study structural features of the prion protein, to probe how truncated forms participate in misfolding or aggregation, and to test interactions with antibodies or other molecules. Detection commonly involves immunoblotting after protease digestion, with antibodies recognizing epitopes within or flanking the retained fragment, and may also employ mass spectrometry to define precise fragment boundaries.

Terminology and interpretation: Because PrPfr is not a fixed term, researchers should refer to the exact proteolysis conditions and the sequence included in the fragment when interpreting results. The term often serves as a practical shorthand in discussions of protease-resistant PrP species before a definitive sequence is reported.

See also: Prion protein, PrP C, PrP Sc.