Figure 1

Prevention and reversion of protein aggregation by chaperones and proteases in eubacteria. Protein aggregation is caused by misfolded protein species and can be facilitated by overproduction of heterologous proteins, thermal or oxidative stress and protein mutations affecting protein folding. Formation of protein aggregates can be prevented either by Hsp60 or Hsp70-mediated refolding of aggregation-prone substrates or by removal of the misfolded protein species by proteolytic systems (Lon, ClpAP, ClpCP/MecA). High levels of misfolded proteins can overburden the capacity of chaperones and proteases, leading to protein aggregation. Aggregated proteins are rescued by the Hsp104/Hsp70 or the ClpB/DnaK bi-chaperone systems. Protein aggregates can also be solubilized by ClpCP/MecA or ClpAP (+/- ClpS) resulting in substrate hydrolysis.