Insights into Chaperones♦
Ontology highlight
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PROVIDER: S-EPMC3258918 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description: Not available
| S-EPMC3258957 | biostudies-literature
Project description:LonA proteases and ClpB chaperones are key components of the protein quality control system in bacterial cells. LonA proteases form a unique family of ATPases associated with diverse cellular activities (AAA+ ) proteins due to the presence of an unusual N-terminal region comprised of two domains: a ?-structured N domain and an ?-helical domain, including the coiled-coil fragment, which is referred to as HI(CC). The arrangement of helices in the HI(CC) domain is reminiscent of the structure of the H1 domain of the first AAA+ module of ClpB chaperones. It has been hypothesized that LonA proteases with a single AAA+ module may also contain a part of another AAA+ module, the full version of which is present in ClpB. Here, we established and tested the structural basis of this hypothesis using the known crystal structures of various fragments of LonA proteases and ClpB chaperones, as well as the newly determined structure of the Escherichia coli LonA fragment (235-584). The similarities and differences in the corresponding domains of LonA proteases and ClpB chaperones were examined in structural terms. The results of our analysis, complemented by the finding of a singular match in the location of the most conserved axial pore-1 loop between the LonA NB domain and the NB2 domain of ClpB, support our hypothesis that there is a structural and functional relationship between two coiled-coil fragments and implies a similar mechanism of engagement of the pore-1 loops in the AAA+ modules of LonAs and ClpBs.
| S-EPMC6722904 | biostudies-literature
Project description:RuBisCO is the most abundant enzyme in nature, catalyzing the fixation of CO2 in photosynthesis. Its common form consists of eight RbcL and eight RbcS subunits, the assembly of which requires a series of chaperones that include RbcX and RuBisCO accumulation factor 1 (Raf1). To understand how these RuBisCO-specific chaperones function during cyanobacterial RbcL8RbcS8 (L8S8) holoenzyme formation, we solved a 3.3-Å cryo-electron microscopy structure of a 32-subunit RbcL8Raf18RbcX16 (L8F8X16) assembly intermediate from Anabaena sp. PCC 7120. Comparison to the previously resolved L8F8 and L8X16 structures together with biochemical assays revealed that the L8F8X16 complex forms a rather dynamic structural intermediate, favoring RbcS displacement of Raf1 and RbcX. In vitro assays further demonstrated that both Raf1 and RbcX function to regulate RuBisCO condensate formation by restricting CcmM35 binding to the stably assembled L8S8 holoenzymes. Combined with previous findings, we propose a model on how Raf1 and RbcX work in concert to facilitate, and regulate, cyanobacterial RuBisCO assembly as well as disassembly of RuBisCO condensates.
| S-EPMC9485235 | biostudies-literature
Project description: Not available
| S-EPMC2667785 | biostudies-literature