Role of Escherichia coli Curli Operons in Directing Amyloid Fiber Formation

Abstract

Amyloid is associated with debilitating human ailments including Alzheimer's and prion diseases. Biochemical, biophysical, and imaging analyses revealed that fibers produced by Escherichia coli called curli were amyloid. The CsgA curlin subunit, purified in the absence of the CsgB nucleator, adopted a soluble, unstructured form that upon prolonged incubation assembled into fibers that were indistinguishable from curli. In vivo, curli biogenesis was dependent on the nucleation-precipitation machinery requiring the CsgE and CsgF chaperone-like and nucleator proteins, respectively. Unlike eukaryotic amyloid formation, curli biogenesis is a productive pathway requiring a specific assembly machinery.

Cutting Edge Structural Protein from the Jaws of Nereis virens

“…Two major size variants of Nvjp-1 were consistently detected in all cDNA preparations, consisting of the larger NVjp-1a and a potential truncation product, NVjp-1b. Alignment of sequences from all clones revealed an additional variant similar to NVjp1a (hereafter termed "NVjp-1a 1 and NVjp-1a 2 "), which consisted of the deletion of two GH repeats (residues [40][41][42][43] and an insertion of one additional GYGGHG repeat (residues 83-88, based on the sequence of NVjp-1a 1 ). The combined frequencies of NVjp-1a 1 , NVjp-1b, and NVjp-1a 2 from all cDNA preparations were 0.56, 0.33, and 0.11, respectively.…”

Beta-amyloid deposition and Alzheimer's type changes induced by Borrelia spirochetes

“…Recent observations show that several bacteria contain amyloidogenic proteins [5,15,19,[21][22][23]26]. Analysis of the periplasmic outer membrane lipoprotein -OsmB -of Escherichia coli showed a similarity in amino acid sequences to A␤ peptide [15].…”

“…Analysis of the periplasmic outer membrane lipoprotein -OsmB -of Escherichia coli showed a similarity in amino acid sequences to A␤ peptide [15]. Recent biochemical, biophysical, and imaging analyses revealed that fibers produced by E. coli, termed "curly" were composed of amyloid [5]. It was suggested that several types of spirochetes may be involved in AD, and also that amyloidogenic proteins may be an integral part of spirochetes, which may, therefore, play a role in amyloidogenesis in AD [18][19][20][21][22][23][24][25]31].…”

“…Intriguingly, the clinical and pathological hallmarks of AD are present in dementia paralytica in the tertiary stage of syphilis caused by the spirochete Treponema pallidum [2,3,27]. Recent observations have shown that several bacteria contain amyloidogenic proteins, including spirochetes [5,15,19,22,23,26]. The outer surface protein (OspA) of Borrelia burgdorferi spirochete has been shown to induce amyloid fibrils in vitro, similar to human amyloid [26].…”

Rapid Generation of Amyloid from Native Proteins <em>In vitro</em>

“…Accordingly, an increasing number of functional amyloids, which participate in various important cellular processes, have been discovered in recent years. For example, bacteria assemble amyloids to form biofilm and spore structures that are critical for their survival and pathogenesis [6][7][8][9] . Peptide hormones form amyloid deposits during storage within mammalian secretory granules before being released, further implying that the protein amyloid form can serve beneficial biological functions 6,10,11 .…”