Structural changes in a hydrophobic domain of the prion protein induced by hydration and by ala-->Val and pro-->Leu substitutions.
X-ray diffraction was used to study the structure of assemblies formed by synthetic peptide fragments of the prion protein (PrP) that include the hydrophobic domain implicated in the Gerstmann-Sträussler-Scheinker (GSS) mutation (P102L). The effects of hydration on polypeptide assembly and of Ala-->Val substitutions in the hydrophobic domain were characterized. Synthetic peptides included: (i) Syrian hamster (SHa) hydrophobic core, SHa106-122 (KTNMKHMAGAAAAGAVV); (ii) SHa104-122(3A-V), with A-->V mutations at 113, 115 and 118 (KPKTNMKHMVGVAAVGAVV); (iii) mouse (Mo) wild-type sequence of the N-terminal hydrophobic domain, Mo89-143WT; and (iv) the same mouse sequence with leucine substitution for proline at residue number 101, Mo89-143(P101L). Samples of SHa106-122 that formed assemblies while drying under ambient conditions showed X-ray patterns indicative of 33 A thick slab-like structures having extensive H-bonding and intersheet stacking. By contrast, lyophilized peptide that was equilibrated against 100 % relative humidity showed assemblies with only a few layers of beta-sheets. The Ala-->Val substitutions in SHa104-122 and Mo89-143(P101L) resulted in the formation of 40 A wide, cross-beta fibrils. Observation of similar size beta-sheet fibrils formed by peptides SHa104-122(3A-V) and the longer Mo89-143(P101L) supports the notion that the hydrophobic sequence forms a template or core that promotes the beta-folding of the longer peptide. The substitution of amino acids in the mutants, e.g. 3A-->V and P101L, enhances the folding of the peptide into compact structural units, significantly enhancing the formation of the extensive beta-sheet fibrils.
Inouye
H
H
Department of Biology, Boston College, Chestnut Hill, MA 02467-3811, USA. inouye@amy.bc.edu
Bond
J
J
Baldwin
M A
MA
Ball
H L
HL
Prusiner
S B
SB
Kirschner
D A
DA
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D006224:Cricetinae; D016098:Gerstmann-Straussler-Scheinker Disease / Q000235:genetics*; D006801:Humans; D006860:Hydrogen Bonding; D008647:Mesocricetus; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011328:Prions / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D014867:Water / Q000378:metabolism*; D014961:X-Ray Diffraction
D010446:Peptide Fragments; D011328:Prions; D014867:Water