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J Biol Chem. 2013 Jun 14;288(24):17559-68. doi: 10.1074/jbc.M113.453605. Epub 2013 Apr 30.

Isolation, characterization, and aggregation of a structured bacterial matrix precursor.

Author information

1
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Abstract

Biofilms are surface-associated groups of microbial cells that are embedded in an extracellular matrix (ECM). The ECM is a network of biopolymers, mainly polysaccharides, proteins, and nucleic acids. ECM proteins serve a variety of structural roles and often form amyloid-like fibers. Despite the extensive study of the formation of amyloid fibers from their constituent subunits in humans, much less is known about the assembly of bacterial functional amyloid-like precursors into fibers. Using dynamic light scattering, atomic force microscopy, circular dichroism, and infrared spectroscopy, we show that our unique purification method of a Bacillus subtilis major matrix protein component results in stable oligomers that retain their native α-helical structure. The stability of these oligomers enabled us to control the external conditions that triggered their aggregation. In particular, we show that stretched fibers are formed on a hydrophobic surface, whereas plaque-like aggregates are formed in solution under acidic pH conditions. TasA is also shown to change conformation upon aggregation and gain some β-sheet structure. Our studies of the aggregation of a bacterial matrix protein from its subunits shed new light on assembly processes of the ECM within bacterial biofilms.

KEYWORDS:

Amyloid Precursor Protein; Bacillus; Biofilm; Extracellular Matrix; Extracellular Matrix Proteins; Microbiology; Protein Aggregation

PMID:
23632024
PMCID:
PMC3682555
DOI:
10.1074/jbc.M113.453605
[Indexed for MEDLINE]
Free PMC Article

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