Betabellins 15D and 16D, de Novo designed beta-sandwich proteins that have amyloidogenic properties.
The betabellin structure is a de novo designed beta-sandwich protein consisting of two 32-residue beta-sheets packed against one another by hydrophobic interactions. d-Amino acid residues are used to energetically favor formation of type-I' beta turns. Air oxidation of betabellin 15S (B15S) (HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, where p denotes d-Pro, h denotes d-His, and k denotes d-Lys) yields betabellin 15D (B15D), a 64-residue disulfide-bridged protein. The amino acid sequence of B15D contains a conformationally constrained d-Pro residue at the i + 1 position of each type-I' beta turn. To test whether d-Pro residues are necessary for folding at these positions, the six d-Pro residues of B15D are replaced by d-Ala residues in betabellin 16D (B16D). Previously, transmission electron microscopy showed that B15D forms unbranched, 35-A wide fibrils that associate into bundles in 5.0 mM 3-(N-morpholino)propanesulfonate and 250 mM NaCl at pH 7; under these conditions, B16D forms ribbon-like assemblies. The B15D fibrils resemble the protofilaments that constitute amyloid fibrils. The present studies show that both B15D and B16D have characteristics of amyloidogenic proteins: the unbranched fibrils and ribbons stained with Congo red and displayed a green birefringence, exhibited a cross-beta structure, and bound 1-anilino-8-naphthalenesulfonate. Thus, these de novo designed beta-sandwich proteins should provide useful models for studying the mechanism of amyloid protofilament formation and assembly into amyloid fibrils and for designing potential inhibitors of amyloidogenesis.
Lim
A
A
Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA.
Makhov
A M
AM
Bond
J
J
Inouye
H
H
Connors
L H
LH
Griffith
J D
JD
Erickson
B W
BW
Kirschner
D A
DA
Costello
C E
CE
D000595:Amino Acid Sequence; D000682:Amyloid; D000686:Amyloidosis; D000817:Anilino Naphthalenesulfonates; D004396:Coloring Agents; D003224:Congo Red; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D011994:Recombinant Proteins; D013050:Spectrometry, Fluorescence; D014961:X-Ray Diffraction
D000682:Amyloid; D000817:Anilino Naphthalenesulfonates; D004396:Coloring Agents; D009842:Oligopeptides; D011506:Proteins; D011994:Recombinant Proteins; C114709:betabellin 15; C400381:betabellin 16D; D003224:Congo Red