| Hsp93 |
| Hsp93 is a component of import complexes |
Anti-Toc75 antibody coimmunoprecipitated Hsp93 |
(Nielsen et al., 1997) |
No cross-linker used, solubilized with 1% decylmaltoside |
| (Akita et al., 1997) |
Cross-linked with dithiobis(succinimidylpropionate) (DSP) |
| Anti-cpHsc70 antibody coimmunoprecipitated Hsp93, Toc75, and Toc34 |
(Su and Li, 2010) |
Toc75 identified by both immunoblotting and mass spectrometry |
| Hsp93 cofractionated with other translocon components, including Toc75, in sucrose density gradients |
(Nielsen et al., 1997) |
|
| Anti-Toc34 antibody coimmunoprecipitated Hsp93, Toc75, and Tic20 |
(Kouranov et al., 1998) |
Untreated chloroplasts or chloroplasts cross-linked in the presence of 400 nM preprotein; solubilized with 1% Triton X-100 |
| Hsp93 is a component of complexes actively engaged in protein import |
Bound prRBCS, prLHCP, and prPC, but not outer-membrane OEP14, were coimmunoprecipitated by anti-Hsp93 antibodies |
(Nielsen et al., 1997) |
No cross-linker used, solubilized with 1% decylmaltoside |
| PrRBCS was coimmunoprecipitated by anti-Hsp93 antibodies in import time course |
(Chou et al., 2003) |
Cross-linked with 0.5 mM DSP and solubilized with Triton X-100 |
| Translocating prRBCS and prL11 coimmunoprecipitated by anti-Hsp93 antibodies |
(Su and Li, 2010) |
If preproteins added after chloroplast lysis, no coimmunoprecipitation was observed |
| Hsp93 detected in soluble import complexes purified using preprotein-GST fusions and GSH beads |
(Rosano et al., 2011) |
Recombinant preprotein used is pea ferredoxin-NADP reductase transit peptide fused to GST |
| Anti-Hsp93 antibody immunoprecipitated large (>700 kD on SDS-PAGE) cross-linked complex containing preproteins |
(Akita et al., 1997) |
|
|
hsp93 mutant chloroplasts are defective in protein import into chloroplasts |
In vitro translated preproteins imported into chloroplasts isolated from mutant and wild-type plants |
(Constan et al., 2004) |
hsp93V-knockout Arabidopsis plants |
| (Kovacheva et al., 2005
|
hsp93V-knockout Arabidopsis plants; both prRBCS (photosynthetic) and prL11 (nonphotosynthetic) preproteins used |
| (Kovacheva et al., 2007; Flores-Pérez et al., 2016)
|
Double mutants of hsp93V knockout and hsp93III knockdown |
| (Su and Li, 2010) |
hsp93V-knockout Arabidopsis plants have an import defect; the cphsc70-1 hsp93V double mutant has a more severe import defect |
| Transient expression of preproteins in protoplasts isolated from hsp93V mutant and wild-type plants |
(Lee et al., 2018) |
|
| Association of Hsp93 with the inner envelope membrane is important for its functions |
Hsp93V-∆N deletion mutant cannot complement the hsp93V null mutant; AtHsp93V-∆N has the same ATPase activity but severely reduced membrane and Tic110 association |
(Chu and Li, 2012) |
Hsp93V-∆N is an Hsp93V mutant with the N-terminal domain deleted |
| Hsp93 directly binds transit peptides |
Escherichia coli expressed recombinant ClpC2 (i.e. Hsp93III) and ClpD specifically bind preproteins in vitro |
(Rosano et al., 2011) |
The preprotein used is pea ferredoxin-NADP reductase transit peptide fused to GST |
| Transit peptides of translocating preproteins directly cross-linked to Hsp93 at early stages of active import into chloroplasts |
(Huang et al., 2016) |
Two different preproteins, prRBCS and prTic40, were used |
| Hsp90C |
| Hsp90C is a component of complexes containing translocating preproteins |
Hsp90C, together with Toc75 and Tic110, specifically copurified with bound preproteins, prRBCS or prTic40 |
(Inoue et al., 2013) |
|
| Inhibition of Hsp90 ATPase activity reduces protein import |
Treatment of isolated chloroplasts with the Hsp90 inhibitor, radicicol, reversibly inhibits ATP-dependent protein import |
(Inoue et al., 2013) |
|
| cpHsp70 |
| Hsp70 binds to chloroplast transit peptides |
Hsp70 binds prSSU and prFd transit peptides |
(Ivey et al., 2000) |
Both DnaK and Hsc70 isoforms of Hsp70 were tested |
| Transit peptides containing Hsp70 binding elements were targeted to chloroplasts, whereas those without were not |
(Chotewutmontri and Bruce, 2015) |
|
| cpHsp70 is essential in Arabidopsis and Physcomitrella
|
Targeted knockout of cpHsp70-2 in the moss, Physcomitrella, is lethal |
(Shi and Theg, 2010) |
Physcomitrella has three cpHsp70 genes, knockout of cpHsp70-1 and cpHsp70-3 are without obvious phenotype |
| T-DNA insertion knockout of both copies of cpHsp70 in Arabidopsis is lethal |
(Su and Li, 2010) |
Individual knockouts are not lethal |
| Reduced cpHsp70 slows protein import into chloroplasts |
Knockouts of individual cpHsp70 genes in Arabidopsis display reduced rates of protein import in young chloroplasts |
(Su and Li, 2010) |
|
| Temperature-sensitive mutants of moss cpHsp70-2 display reduced rates of protein import after a heat shock |
(Shi and Theg, 2010) |
Two different temperature-sensitive mutants behaved similarly |
| cpHsp70 is a component of import complexes |
Anti-Hsp70 antibodies coimmunoprecipitate Hsp93 and Tic40 in moss |
(Shi and Theg, 2010) |
In CGE knockdown mutant with preproteins added |
|
Anti-cpHsp70 antibodies coimmunoprecipitate Toc75, Toc34, Tic110, Tic40, and Hsp93 in pea (Pisum sativum) chloroplasts |
(Su and Li, 2010) |
No preprotein addition, indicating that cpHsp70 is preassembled in import complexes |
| cpHsp70 is in complexes containing translocating preproteins |
Anti-cpHsp70 antibodies coimmunoprecipitate translocating preproteins, prSSU and prCGE, in moss |
(Shi and Theg, 2010) |
In CGE knockdown mutant with preprotein added |
|
Anti-cpHsp70 antibodies coimmunoprecipitate translocating preproteins, prRBCS and prL11, in pea chloroplasts |
(Su and Li, 2010) |
|
| cpHsp70 cochaperones are required for chloroplast protein import |
CGE knockdown mutants display reduced rates of chloroplast protein import in moss |
(Shi and Theg, 2010) |
|
| Change of cpHsp70 Km for ATP hydrolysis translates into change of ATP requirement for protein import |
Chloroplasts harboring cpHsp70 with a 2.6-fold increased Km for ATP hydrolysis required 3.1 times as much ATP to import prSSU |
(Liu et al., 2014) |
Two different cpHsp70 amino acid substitutions behaved similarly |
