Amyloidogenic properties of transthyretin-like protein (TLP) from Escherichia coli

We report the amyloid-like properties of Escherichia coli transthyretin-like protein (TLP). TLP is 32% homologous to human transthyretin (hTTR), and is also tetrameric. In contrast to hTTR, TLP does not bind thyroxine. TLP orthologues are found in several prokaryotes, lower eukaryotes and vertebrates. TLP carries a signal peptide that targets the protein to the periplasmic space. We found that TLP and hTTR tetramers dissociate into monomers under similar conditions, although TLP monomers have different association properties. Like hTTR, TLP forms aggregates, small fibrillar structures of 8nm width, and annular structures of 8nm diameter which present amyloid-like properties and are toxic to cells.