1H-NMR structural studies of a cystine-linked peptide containing residues 71-93 of transthyretin and effects of a Ser84 substitution implicated in familial amyloidotic polyneuropathy.
The Ile-->Ser84 substitution in the thyroid hormone transport protein transthyretin is one of over 50 variations found to be associated with familial amyloid polyneuropathy, a hereditary type of lethal amyloidosis. Using a peptide analogue of the loop containing residue 84 in transthyretin, we have examined the putative local structural effects of this substitution using 1H-NMR spectroscopy. The peptide, containing residues 71-93 of transthyretin with its termini linked via a disulfide bond, was found to possess the same helix-turn motif as in the corresponding region of the crystallographically derived structure of transthyretin in 20% trifluoroethanol (TFE) solution. It therefore, represents a useful model with which to examine the effects of amyloidogenic substitutions. In a peptide analogue containing the Ile84-->Ser substitution it was found that the substitution does not greatly disrupt the overall three-dimensional structure, but leads to minor local differences at the turn in which residue 84 is involved. Coupling constant and NOE measurements indicate that the helix-turn motif is still present, but differences in chemical shifts and amide-exchange rates reflect a small distortion. This is in keeping with observations that several other mutant forms of transthyretin display similar subunit interactions and those that have been structurally analysed possess a near native structure. We propose that the Ser84 mutation induces only subtle perturbations to the transthyretin structure which predisposes the protein to amyloid formation.
Wilce
J A
JA
Department of Chemistry/Biochemistry, University of Western Australia, Nedlands, Australia.
Salvatore
D
D
Wade
J D
JD
Craik
D J
DJ
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017772:Amyloid Neuropathies / Q000378:metabolism*; D003553:Cystine / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011228:Prealbumin / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011522:Protons; D012694:Serine / Q000737:chemistry*
D011228:Prealbumin; D011522:Protons; D012694:Serine; D003553:Cystine