| 1. |
- Gustavsson, Niklas, et al.
(författare)
-
Methionine sulfoxidation of the chloroplast small heat shock protein and conformational changes in the oligomer
- 1999
-
Ingår i: Protein Science. - : Wiley. - 1469-896X .- 0961-8368. ; 8:11, s. 2506-2512
-
Tidskriftsartikel (refereegranskat)abstract
- The small heat shock proteins (sHsps), which counteract heat and oxidative stress in an unknown way, belong to a protein family of sHsps and alpha-crystallins whose members form large oligomeric complexes. The chloroplast-localized sHsp, Hsp21, contains a conserved methionine- rich sequence, predicted to form an amphipatic helix with the methionines situated along one of its sides. Here, we report how methionine sulfoxidation was detected by mass spectrometry in proteolytically cleaved peptides that were produced from recombinant Arabidopsis thaliana Hsp21, which had been treated with varying concentrations of hydrogen peroxide. Sulfoxidation of the methionine residues in the conserved amphipatic helix coincided with a significant conformational change in the Hsp21 protein oligomer.
|
|
| 2. |
- Gustavsson, Niklas, et al.
(författare)
-
Substitution of conserved methionines by leucines in chloroplast small heat shock protein results in loss of redox-response but retained chaperone-like activity
- 2001
-
Ingår i: Protein Science. - 1469-896X. ; 10:9, s. 1785-1793
-
Tidskriftsartikel (refereegranskat)abstract
- During evolution of land plants, a specific motif occurred in the N-terminal domain of the chloroplast-localized small heat shock protein, Hsp21: a sequence with highly conserved methionines, which is predicted to form an amphipathic -helix with the methionines situated along one side. The functional role of these conserved methionines is not understood. We have found previously that treatment, which causes methionine sulfoxidation in Hsp21, also leads to structural changes and loss of chaperone-like activity. Here, mutants of Arabidopsis thaliana Hsp21 protein were created by site-directed mutagenesis, whereby conserved methionines were substituted by oxidation-resistant leucines. Mutants lacking the only cysteine in Hsp21 were also created. Protein analyses by nondenaturing electrophoresis, size exclusion chromatography, and circular dichroism proved that sulfoxidation of the four highly conserved methionines (M49, M52, M55, and M59) is responsible for the oxidation-induced conformational changes in the Hsp21 oligomer. In contrast, the chaperone-like activity was not ultimately dependent on the methionines, because it was retained after methionine-to-leucine substitution. The functional role of the conserved methionines in Hsp21 may be to offer a possibility for redox control of chaperone-like activity and oligomeric structure dynamics.
|
|
