| 1. |
- Andersson, Fredrik, 1977, et al.
(författare)
-
Cyanobacterial ClpC/HSP100 protein displays intrinsic chaperone activity
- 2006
-
Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 281:9, s. 5468-5475
-
Tidskriftsartikel (refereegranskat)abstract
- HSP100 proteins are molecular chaperones that belong to the broader family of AAA+ proteins ( ATPases associated with a variety of cellular activities) known to promote protein unfolding, disassembly of protein complexes and translocation of proteins across membranes. The ClpC form of HSP100 is an essential, highly conserved, constitutively expressed protein in cyanobacteria and plant chloroplasts, and yet little is known regarding its specific activity as a molecular chaperone. To address this point, ClpC from the cyanobacterium Synechococcus elongatus (SyClpC) was purified using an Escherichia coli-based overexpression system. Recombinant SyClpC showed basal ATPase activity, similar to that of other types of HSP100 protein in non-photosynthetic organisms but different to ClpC in Bacillus subtilis. SyClpC also displayed distinct intrinsic chaperone activity in vitro, first by preventing aggregation of unfolded polypeptides and second by resolubilizing and refolding aggregated proteins into their native structures. The refolding activity of SyClpC was enhanced 3-fold in the presence of the B. subtilis ClpC adaptor protein MecA. Overall, the distinctive ClpC protein in photosynthetic organisms indeed functions as an independent molecular chaperone, and it is so far unique among HSP100 proteins in having both "holding" and disaggregase chaperone activities without the need of other chaperones or adaptor proteins.
|
|
| 2. |
- Barker-Astrom, K., et al.
(författare)
-
Chlorosis during nitrogen starvation is altered by carbon dioxide and temperature status and is mediated by the ClpP1 protease in Synechococcus elongatus
- 2005
-
Ingår i: Archives of Microbiology. - : Springer Science and Business Media LLC. - 0302-8933 .- 1432-072X. ; 183:1, s. 66-69
-
Tidskriftsartikel (refereegranskat)abstract
- The interactive effects of inorganic carbon status, temperature and light on chlorosis induced by nitrogen deficiency, and the roles of Clp proteases in this process were investigated. In wild-type cultures grown in high or ambient CO2, following transfer to media lacking combined nitrogen, phycocyanin per cell dropped primarily through dilution of the pigment through cell division, and also suffered variable degrees of net degradation. When grown at high CO2 (5%), chlorophyll (Chl) suffered net degradation to a greater extent than phycocyanin. In marked contrast, growth at ambient CO2 resulted in Chl per cell dropping through dilution. Conditions that drove net Chl degradation in the wild-type resulted in little or no net Chl degradation in a clpPI inactivation mutant, with Chl content dropping largely through growth dilution in the mutant. The chlorotic response of a clpPII inactivation strain was nearly the same as that of wild-type, although phycocyanin degradation may have been slightly accelerated in the former.
|
|
| 3. |
- Eriksson, Martin, 1970, et al.
(författare)
-
Community-Level Analysis of psbA Gene Sequences and Irgarol Tolerance in Marine Periphyton
- 2009
-
Ingår i: Applied and Environmental Microbiology. - Washington, D.C. : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 75:4, s. 897-906
-
Tidskriftsartikel (refereegranskat)abstract
- This study analyzes psbA gene sequences, predicted D1 protein sequences, species relative abundance, and pollution-induced community tolerance in marine periphyton communities exposed to the antifouling compound Irgarol 1051. The mechanism of action of Irgarol is the inhibition of photosynthetic electron transport at photosystem II by binding to the D1 protein. The metagenome of the communities was used to produce clone libraries containing fragments of the psbA gene encoding the D1 protein. Community tolerance was quantified with a short-term test for the inhibition of photosynthesis. The communities were established in a continuous flow of natural seawater through microcosms with or without added Irgarol. The selection pressure from Irgarol resulted in an altered species composition and an inducted community tolerance to Irgarol. Moreover, there was a very high diversity in the psbA gene sequences in the periphyton, and the composition of psbA and D1 fragments within the communities was dramatically altered by increased Irgarol exposure. Even though tolerance to this type of compound in land plants often depends on a single amino acid substitution (Ser(264)-> Gly) in the D1 protein, this was not the case for marine periphyton species. Instead, the tolerance mechanism likely involves increased degradation of D1. When we compared sequences from low and high Irgarol exposure, differences in nonconserved amino acids were found only in the so-called PEST region of D1, which is involved in regulating its degradation. Our results suggest that environmental contamination with Irgarol has led to selection for high-turnover D1 proteins in marine periphyton communities at the west coast of Sweden.
|
|
| 4. |
- Andersson, Fredrik, 1977, et al.
(författare)
-
Structure and function of a novel type of ATP-dependent Clp protease.
- 2009
-
Ingår i: The Journal of biological chemistry. - 0021-9258 .- 1083-351X. ; 284:20, s. 13519-32
-
Tidskriftsartikel (refereegranskat)abstract
- The Clp protease is conserved among eubacteria and most eukaryotes, and uses ATP to drive protein substrate unfolding and translocation into a chamber of sequestered proteolytic active sites. The main constitutive Clp protease in photosynthetic organisms has evolved into a functionally essential and structurally intricate enzyme. The model Clp protease from the cyanobacterium Synechococcus consists of the HSP100 molecular chaperone ClpC and a mixed proteolytic core comprised of two distinct subunits, ClpP3 and ClpR. We have purified the ClpP3/R complex, the first for a Clp proteolytic core comprised of heterologous subunits. The ClpP3/R complex has unique functional and structural features, consisting of twin heptameric rings each with an identical ClpP3(3)ClpR(4) configuration. As predicted by its lack of an obvious catalytic triad, the ClpR subunit is shown to be proteolytically inactive. Interestingly, extensive modification to ClpR to restore proteolytic activity to this subunit showed that its presence in the core complex is not rate-limiting for the overall proteolytic activity of the ClpCP3/R protease. Altogether, the ClpP3/R complex shows remarkable similarities to the 20 S core of the proteasome, revealing a far greater degree of convergent evolution than previously thought between the development of the Clp protease in photosynthetic organisms and that of the eukaryotic 26 S proteasome.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Clarke, Adrian K, 1964, et al.
(författare)
-
The ATP-dependent Clp protease in chloroplasts of higher plants
- 2005
-
Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 123:4, s. 406-412
-
Tidskriftsartikel (refereegranskat)abstract
- The best-known proteases in plastids are those that belong to families common to eubacteria. One of the first identified was the ATP-dependent caseinolytic protease (Clp), whose structure and function have been well characterized in Escherichia coli. Plastid Clp proteins in higher plants are surprisingly numerous and diverse, with at least 16 distinct Clp proteins in the model plant Arabidopsis thaliana. Multiple paralogues exist for several of the different types of plastid Clp protein, with the most extreme being five for the proteolytic subunit ClpP. Both biochemical and genetic studies have recently begun to reveal the intricate structural interactions between the various Clp proteins, and their importance for chloroplast function and plant development. Much of the recent data suggests that the function of many of the Clp proteins probably affects more specific processes within chloroplasts, in addition to the more general 'housekeeping' role previously assumed.
|
|
| 8. |
- Eriksson, Martin, 1970, et al.
(författare)
-
A phylogenetic approach to detect selection on the target site of the antifouling compound irgarol in tolerant periphyton communities
- 2009
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 11:8, s. 2065-2077
-
Tidskriftsartikel (refereegranskat)abstract
- Using DNA sequence data for phylogenetic assessment of toxicant targets is a new and promising approach to study toxicant-induced selection in communities. Irgarol 1051 is a photosystem (PS) II inhibitor used in antifouling paint. It inhibits photosynthesis through binding to the D1 protein in PS II, which is encoded by the psbA gene found in genomes of chloroplasts, cyanobacteria and cyanophages. psbA mutations that alter the target protein can confer tolerance to PS II inhibitors. We have previously shown that irgarol induces community tolerance in natural marine periphyton communities and suggested a novel tolerance mechanism, involving the amino acid sequence of a turnover-regulating domain of D1, as contributive to this tolerance. Here we use a large number of psbA sequences of known identity to assess the taxonomic affinities of psbA sequences from these differentially tolerant communities, by performing phylogenetic analysis. We show that periphyton communities have high psbA diversity and that this diversity is adversely affected by irgarol. Moreover, we suggest that within tolerant periphyton the novel tolerance mechanism is present among diatoms only, whereas some groups of irgarol-tolerant cyanobacteria seem to have other tolerance mechanisms. However, it proved difficult to identify periphyton psbA haplotypes to the species or genus level, which indicates that the genomic pool of the attached, periphytic life forms is poorly studied and inadequately represented in international sequence databases.
|
|
| 9. |
|
|
| 10. |
- Koussevitzky, S., et al.
(författare)
-
An Arabidopsis thaliana virescent mutant reveals a role for ClpR1 in plastid development
- 2007
-
Ingår i: Plant Molecular Biology. - : Springer Science and Business Media LLC. - 0167-4412 .- 1573-5028. ; 63:1, s. 85-96
-
Tidskriftsartikel (refereegranskat)abstract
- The ATP-dependent Clp protease has been well-characterized in Escherichia coli, but knowledge of its function in higher plants is limited. In bacteria, this two-component protease consists of a Ser-type endopeptidase ClpP, which relies on the ATP-dependent unfolding activity from an Hsp100 molecular chaperone to initiate protein degradation. In the chloroplasts of higher plants, multiple isoforms of the proteolytic subunit exist, with Arabidopsis having five ClpPs and four ClpP-like proteins termed ClpR predicted in its genome. In this work we characterized an Arabidopsis mutant impaired in one subunit of the chloroplast-localized Clp protease core, ClpR1. clpR1-1, a virescent mutant, carries a pre-mature stop codon in the clpR1 gene, resulting in no detectable ClpR1 protein. The accumulation of several chloroplast proteins, as well as most of the chloroplast-localized Clp protease subunits, is inhibited in clpR1-1. Unexpectedly, some plastid-encoded proteins do not accumulate, although their transcripts accumulate to wild-type levels. Maturation of 23S and 4.5S chloroplast ribosomal RNA (cp-rRNA) is delayed in clpR1-1, and both RNAs accumulate as higher molecular weight precursors. Also, chloroplasts in clpR1-1 are smaller than in wild type and have fewer thylakoid membranes with smaller grana stacks. We propose that a ClpR1-containing activity is required for chloroplast development and differentiation and in its absence both are delayed.
|
|
