Solubilization of protein aggregates by the acid stress chaperones HdeA and HdeB.
The acid stress chaperones HdeA and HdeB of Escherichia coli prevent the aggregation of periplasmic proteins at acidic pH. We show in this report that they also form mixed aggregates with proteins that have failed to be solubilized at acidic pH and allow their subsequent solubilization at neutral pH. HdeA, HdeB, and HdeA and HdeB together display an increasing efficiency for the solubilization of protein aggregates at pH 3. They are less efficient for the solubilization of aggregates at pH 2, whereas HdeB is the most efficient. Increasing amounts of periplasmic proteins draw increasing amounts of chaperone into pellets, suggesting that chaperones co-aggregate with their substrate proteins. We observed a decrease in the size of protein aggregates in the presence of HdeA and HdeB, from very high molecular mass aggregates to 100-5000-kDa species. Moreover, a marked decrease in the exposed hydrophobicity of aggregated proteins in the presence of HdeA and HdeB was revealed by 1,1'-bis(4-anilino)naphtalene-5,5'-disulfonic acid binding experiments. In vivo, during the recovery at neutral pH of acid stressed bacterial cells, HdeA and HdeB allow the solubilization and renaturation of protein aggregates, including those formed by the maltose receptor MalE, the oligopeptide receptor OppA, and the histidine receptor HisJ. Thus, HdeA and HdeB not only help to maintain proteins in a soluble state during acid treatment, as previously reported, but also assist, both in vitro and in vivo, in the solubilization at neutral pH of mixed protein-chaperone aggregates formed at acidic pH, by decreasing the size of protein aggregates and the exposed hydrophobicity of aggregated proteins.
Malki
Abderrahim
A
Stress Molecules Laboratory, Institut Jacques Monod, Université Paris 7, 2 place Jussieu, 75005 Paris, France.
Le
Hai-Tuong
HT
Milles
Sigrid
S
Kern
Renée
R
Caldas
Teresa
T
Abdallah
Jad
J
Richarme
Gilbert
G
D000143:Acids / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry; D033902:Periplasmic Binding Proteins / Q000737:chemistry; D033903:Periplasmic Proteins / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D013379:Substrate Specificity
D000143:Acids; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D018832:Molecular Chaperones; D033902:Periplasmic Binding Proteins; D033903:Periplasmic Proteins; C084501:hdeA protein, E coli; C084502:hdeB protein, E coli; C018963:histidine-binding protein; D006639:Histidine