Soluble complexes of amylod β peptide and peptidyl prolyl isomerase chaperone and methods of making and using them

A recombinant polypeptide which is soluble to at least 100 nM in a solution which has a pH of 7.4 and consists of 20 nM sodium phosphate and 150 nM sodium chloride, said recombinant polypeptide comprising:

• an amyloid β(Aβ) peptide,
• a peptidic linker, and
• a peptidyl prolyl isomerase chaperone.

A recombinantly-produced fusion polypeptide comprising:

• an amyloid β(Aβ) peptide, and
• an FKBP chaperone polypeptide, wherein said FKBP chaperone polypeptide is selected from the group consisting of FkpA, SlyD, and trigger factor.

An expression vector comprising:

• at least one nucleic acid sequence encoding an amyloid β(Aβ) peptide,
• at least one nucleic acid sequence encoding a peptidic linker, and
• at least one nucleic acid sequence encoding an FKBP chaperone selected from the group consisting of FkpA, SlyD, and trigger factor.

A method for producing a soluble amyloid β(Aβ) peptide-chaperone protein comprising:

• incubating a protein comprising Aβ peptide covalently linked to a peptidyl prolyl isomerase chaperone in a nonphysiological buffer wherein both the Aβ peptide and the chaperone are solubilized, and
• adjusting the buffer to physiological conditions wherein the Aβ-chaperone protein formed is soluble to at least 100 nM, said buffer at physiological conditions comprising a pH of 7.4, 20 mM sodium phosphate, and 150 mM sodium chloride.