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Stability and fibril formation properties of human and fish transthyretin, and of the Escherichia coli transthyretin‐related protein
Author(s) -
Lundberg Erik,
Olofsson Anders,
Westermark Gunilla T.,
SauerEriksson A. Elisabeth
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.06936.x
Subject(s) - fibril , transthyretin , thioflavin , chemistry , amyloid (mycology) , biophysics , congo red , escherichia coli , protein structure , negative stain , biochemistry , crystallography , biology , organic chemistry , adsorption , electron microscope , medicine , inorganic chemistry , physics , disease , pathology , gene , optics , alzheimer's disease , endocrinology
Human transthyretin (hTTR) is one of several proteins known to cause amyloid disease. Conformational changes in its native structure result in aggregation of the protein, leading to insoluble amyloid fibrils. The transthyretin (TTR)‐related proteins comprise a protein family of 5‐hydroxyisourate hydrolases with structural similarity to TTR. In this study, we tested the amyloidogenic properties, if any, of sea bream TTR (sbTTR) and Escherichia coli transthyretin‐related protein (ecTRP), which share 52% and 30% sequence identity, respectively, with hTTR. We obtained filamentous structures from all three proteins under various conditions, but, interestingly, different structures displayed different tinctorial properties. hTTR and sbTTR formed thin, curved fibrils at low pH (pH 2–3) that bound thioflavin‐T (thioflavin‐T‐positive) but did not stain with Congo Red (CR) (CR‐negative). Aggregates formed at the slightly higher pH of 4.0–5.5 had different morphology, displaying predominantly amorphous structures. CR‐positive material of hTTR was found in this material, in agreement with previous results. ecTRP remained soluble at pH 2–12 at ambient temperatures. By raising of the temperature, fibril formation could be induced at neutral pH in all three proteins. Most of these temperature‐induced fibrils were thicker and straighter than the in vitro fibrils seen at low pH. In other words, the temperature‐induced fibrils were more similar to fibrils seen in vivo . The melting temperature of ecTRP was 66.7 °C. This is approximately 30 °C lower than the melting temperatures of sbTTR and hTTR. Information from the crystal structures was used to identify possible explanations for the reduced thermostability of ecTRP.