Myoglobin forms amyloid fibrils by association of unfolded polypeptide segments

Abstract

Observations that ␤-sheet proteins form amyloid fibrils under at least partially denaturing conditions has raised questions as to whether these fibrils assemble by docking of preformed ␤-structure or by association of unfolded polypeptide segments. By using ␣-helical protein apomyoglobin, we show that the ease of fibril assembly correlates with the extent of denaturation. By contrast, monomeric ␤-sheet intermediates could not be observed under the conditions of fibril formation. These data suggest that amyloid fibril formation from apomyoglobin depends on disordered polypeptide segments and conditions that are selectively unfavorable to folding. However, it is inevitable that such conditions often stabilize protein folding intermediates.

Raft lipids as common components of human extracellular amyloid fibrils

“…The following conditions were used to form fibrils in vitro: A␤(1-40): 10 mg͞ml in 50 mM sodium borate, pH 9.0, at 20°C; MYO(101-118): 5 mg͞ml in 50 mM sodium acetate, pH 5.0, at 65°C; full-length murine SAA1.1: 5 mg͞ml in 50 mM sodium phosphate, pH 3.0, at 37°C; human SAA1.1(2-21): 10 mg͞ml in 50 mM sodium phosphate, pH 1.0, at 20°C; and transthyretin: 10 mg͞ml in 50 mM sodium acetate, pH 4.4, at 37°C. The presence of amyloid structure was confirmed with CR and negative-stain electron microscopy (20).…”

“…The myoglobin fragment MYO(101-118) and serum amyloid A (SAA)1.1 (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) were obtained from Jerini (Berlin). Transthyretin was a gift from M. Krebs and C. Robinson, (University of Cambridge, Cambridge, U.K.) The coding region of full-length murine SAA1.1 was cloned in fusion to the gene of the maltose-binding protein in the pMAL-c2X vector (NEB, Beverly, MA) and separated by a cleavage site for tobacco etch virus protease.…”

Parallel β-Sheets and Polar Zippers in Amyloid Fibrils Formed by Residues 10−39 of the Yeast Prion Protein Ure2p

“…NMR, nuclear magnetic resonance; Aβ, β-amyloid peptide; Ure2p 10-39 , residues 10-39 of the Ure2p yeast prion protein; EM, electron microscopy; FMOC, 9-fluorenylmethoxycarbonyl; TFA, trifluoroacetic acid; AFM, atomic force microscopy; MAS, magic-angle spinning; fpRFDR-CT, constant-time finite-pulse radiofrequency-driven recoupling; REDOR, rotational echo double resonance; DSQ, double single-quantum; TPPM, two-pulse phase modulation; CSA, chemical shift anisotropy; MD, molecular dynamics One goal of current efforts to elucidate the molecular structures of amyloid fibrils (1-35) is to identify the intermolecular interactions that determine the details of these structures and make amyloid fibrils a stable structural state for many peptides and proteins despite their diversity of amino acid sequences (36)(37)(38)(39)(40)(41). Recent studies by solid state nuclear magnetic resonance (NMR) of fibrils formed by the β-amyloid (Aβ) peptide associated with Alzheimer's disease (5,13,16,18,24,30,31), by various Aβ fragments (1,3,4,(6)(7)(8)12,21,25), and by other amyloidforming peptides (22) indicate that the β-sheets in amyloid fibrils have structures that tend to maximize contacts among hydrophobic residues when the component peptides contain continuous hydrophobic segments.…”

Amyloidogenic sequences in native protein structures

“…It is believed that many, if not all proteins, can be converted in vitro into amyloid fibrils, given the appropriate conditions. [1][2][3][4][5] Regardless of the size, sequence or structure of the amyloid precursor protein, mature fibrils all appear to share a similar highly organised multimolecular morphology. 6 More than 40 pathological conditions in humans have so far been attributed to amyloid deposition, amongst which are Alzheimer's, Huntingdon's, and Parkinson's diseases, as well as the transmissible spongiform encephalopathies.…”