The deletion of amino acids 114-121 in the TM1 domain of mouse prion protein stabilizes its conformation but does not affect the overall structure.
A mutant of mouse prion protein (PrPC) carrying a deletion of residues 114-121 (PrPDelta114-121) has previously been described to lack convertibility into the scrapie-associated isoform of PrP (PrPSc) and to exhibit a dominant-negative effect on the conversion of wild-type PrPC into PrPSc in living cells. Here we report the characterization of recombinantly expressed PrPDelta114-121 by Fourier-transformation infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopy. The analysis of spectra revealed an increased antiparallel beta-sheet content in the deletion mutant compared to wild-type PrPC. This additional short beta-sheet stabilized the fold of the mutant protein by DeltaDeltaG(0)'=3.4+/-0.3 kJ mol(-1) as shown by chemical unfolding experiments using guanidine hydrochloride. Secondary structure predictions suggest that the additional beta-sheet in PrPDelta114-121 is close to the antiparallel beta-sheet in PrPC. The high-affinity Cu2+-binding site outside the octarepeats, which is located close to the deletion and involves His110 as a ligand, was not affected, as detected by electron paramagnetic resonance (EPR) spectroscopy, suggesting that Cu2+ binding does not contribute to the protection of PrPDelta114-121 from conversion into PrPSc. We propose that the deletion of residues 114-121 stabilizes the mutant protein. This stabilization most likely does not obstruct the interaction of PrPDelta114-121 with PrPSc but represents an energy barrier that blocks the conversion of PrPDelta114-121 into PrPSc.
Thaa
Bastian
B
Fachbereich Biologie, Mathematisch-Naturwissenschaftliche Sektion, Universität Konstanz, 78457 Konstanz, Germany.
Zahn
Ralph
R
Matthey
Ulrich
U
Kroneck
Peter M H
PM
Bürkle
Alexander
A
Fritz
Günter
G
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D018620:PrPSc Proteins / Q000737:chemistry; D000072002:Prion Proteins; D011328:Prions / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017384:Sequence Deletion; D017550:Spectroscopy, Fourier Transform Infrared
D018620:PrPSc Proteins; D000072002:Prion Proteins; D011328:Prions; C512657:Prnp protein, mouse; D003300:Copper