Stress Molecules

During environmental stresses, specific proteins are overexpressed in order to maintain cellular proteins in a soluble form (chaperones, proteases, oxidoreductases).
 

• Chaperone / Peptidase HSP31. We have cloned, purified and characterized this protein as a chaperone and a peptidase. It is likely designed for the solubilization of peptides produced by protein degradation.
• Stress Protein YHBO. We have cloned and purified this stress protein, which belongs to the Pyroccoccus furiosus protease I class. YhbO protects cells against thermal, oxidative and pH stresses, and we are attempting to identify its physiological substrates.
• Novel Thioredoxin, YBBN / TRXSC. We have cloned and characterized YbbN, which has only one cysteine in its active site (Ser-X-X-Cys). To function it uses a second cysteine, distant in the sequence, but close in the 3D. YbbN is involved in the expression of several cytoplasmic and periplasmic proteins.
• Novel Acid-Stress Chaperone HDEB. We are characterizing this novel chaperone HdeB, which is involved in the solubilization of proteins at acidic pH (around pH 3). Thus E. coli contains two acid-stress chaperones, one, HdeA is designed for protein solubilization at pH 2, and the other, HdeB, for protein solubilization at pH 3.
• Multicopy Suppressors Of Protein Aggregation. We have found, amongst 4000 genes, two multicopy suppressors of protein aggregation, protein isoaspartate methyltransferase, and a phosphotransferase transport system, which likely functions by the membrane docking of aggregation-prone proteins.
• Peptide Aptamers That Inhibit Protein Aggregation. We have constructed a bank of peptide aptamers, and are aiming to rescue the defective phenotypes of dnaK, groEL and ClpB mutants or to inhibit aggregation of reporter proteins.
• Translation Accuracy. We have identified the RrmJ methyltransferase that methylates U2552 in the A-site of the 23S ribosomal RNA. U2552 methylation increases the speed of translation, but decreases its accuracy (increase in frameshift and readthrough). We are trying to determine whether this methylation depends on certain physiological conditions, in which case U2552 methylation would be a physiological modulator of translation accuracy.

 

Selection of Publications  

J Biol Chem. 2010 Feb 2. [Epub ahead of print]
Protein aggregation in a mutant deficient in YajL,the bacterial homolog of the parkinsonism-associated protein DJ-1.
Kthiri F, Le HT, Gautier V, Caldas T, Malki A, Landoulsi A, Bohn C, Bouloc P, Richarme G.
Abstract

J Biol Chem. 2008 6;283(20):13679-87. Epub 2008 Mar 20.
Solubilization of protein aggregates by the acid stress chaperones HdeA and HdeB.
Malki A, Le HT, Milles S, Kern R, Caldas T, Abdallah J, Richarme G.
Abstract

J. Bacteriol; 2007 189(24):9140-4. Epub 2007 Oct 12.
YhbO protects cells against multiple stresses.
Abdallah J, Caldas T, Kthiri F, Kern R, Richarme G.
Abstract

J Bacteriol; 2007 Jan;189(2):603-10. Epub 2006 Nov 3.
Escherichia coli HdeB is an acid stress chaperone.
Kern R, Malki A, Abdallah J, Tagourti J, Richarme G.
Abstract

Peptidase activity of the E. coli HSP31 chaperone.
Malki A, Caldas T, Abdallah J, Kern R, Eckey V, Kim SJ, Cha SS, Mori H, Richarme G.
J Biol Chem. 2005. 280, 14420-14426.
Abstract

Last modified 03/14/2011

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