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SUMMARY:Functional amyloid in bacteria - Professor Daniel E. Otzen\, Inter
 disciplinary Nanoscience Center (iNANO) and Department of Molecular Biolog
 y and Genetics\, Aarhus University\, DK
DTSTART:20200124T110000Z
DTEND:20200124T120000Z
UID:TALK137851@talks.cam.ac.uk
CONTACT:Dr Georg Krainer
DESCRIPTION:Many bacteria produce functional amyloid\, i.e. proteins which
  are secreted through dedicated export systems and self-assemble on the ba
 cterial surface\, often with the help of nucleator proteins. These amyloid
  proteins serve a diversity of purposes\, but the most prominent one appea
 rs to be structural stability\; for example\, overexpression of the amyloi
 d-forming protein FapC in Pseudomonas species strengthens bacterial biofil
 m against mechanical insults\, increases hydrophobicity and protects again
 st desiccation. Similar properties are ascribed to the curli-forming prote
 in CsgA from E. coli. Unlike pathological amyloid\, functional amyloid has
  been under evolutionary pressure to self-assemble efficiently (i.e. in a 
 single “fast track”) to very stable higher-order structures. My lab is
  engaged in an effort to understand the molecular basis for these properti
 es in more detail and I will present recent progress in this area.\n\nBoth
  FapC and CsgA consist of multiple imperfect repeats. Stepwise removal of 
 these repeats gradually changes the preferred fibrillation pathway of FapC
  from a mechanism dominated by primary nucleation (the simplest pathway) t
 o one in which fragmentation plays an increasing role\; further\, they sig
 nificantly destabilize the fibrils (as measured by their ability to resist
  dissolution in formic acid). Chemical deanturants such as urea slow down 
 fibrillation by several fold but CsgA can still fibrillate efficiently at 
 6M urea\, testimony to its remarkable stability. In contrast to this\, nat
 urally occurring biosurfactants (rhamnolipids) and outer membrane componen
 ts (lipopolysaccharide) markedly stimulate fibrillation. Nevertheless\, fi
 brillation can be inhibited by naturally occurring fibrillation inhibitors
 \, including plant polyphenols like epigallo catechin gallate (EGCG) and p
 enta-galloyl gallate (PGG)\, which direct FapC to off-pathway oligomeric s
 tructures that eventually forms amorphous aggregates. Thus despite their s
 trong drive to self-assemble\, functional amyloid are still sensitive to t
 he same type of manipulation as their pathological counterparts. 
LOCATION:Department of Chemistry\, Cambridge\, Unilever lecture theatre
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