Applying the tools of chemistry (mass spectrometry and covalent modification by small molecule reagents) to the detection of prions and the study of their structure

摘要

Prions are molecular pathogens, able to convert a normal cellular prion protein (PrPC) into a prion (PrPSc). The information necessary for this conversion is contained in the conformation of PrPSc. Mass spectrometry (MS) and small-molecule covalent reactions have been used to study prions. Mass spectrometry has been used to detect and quantitate prions in the attomole range (10?18 mole). MS-based analysis showed that both possess identical amino acid sequences, one disulfide bond, a GPI anchor, asparagine-linked sugar antennae, and unoxidized methionines. Mass spectrometry has been used to define elements of the secondary and tertiary structure of wild-type PrPSc and GPI-anchorless PrPSc. It has also been used to study the quaternary structure of the PrPSc multimer. Small molecule reagents react differently with the same lysine in the PrPC conformation than in the PrPSc conformation. Such differences can be detected by Western blot using mAbs with lysine-containing epitopes, such as 3F4 and 6D11. This permits the detection of PrPSc without the need for proteinase K pretreatment and can be used to distinguish among prion strains. These results illustrate how two important chemical tools, mass spectrometry and covalent modification by small molecules, are being applied to the detection and structural study of prions. Furthermore these tools are or can be applied to the study of the other protein misfolding diseases such as lzheimer Disease, Parkinson Disease, or ALS.