scholarly journals The molecular chaperone Hsp90 delivers precursor proteins to the chloroplast import receptor Toc64

2006 ◽  
Vol 25 (9) ◽  
pp. 1836-1847 ◽  
Author(s):  
Soumya Qbadou ◽  
Thomas Becker ◽  
Oliver Mirus ◽  
Ivo Tews ◽  
Jürgen Soll ◽  
...  
Keyword(s):  
Molecular Chaperone ◽  
Chloroplast Import ◽  
Precursor Proteins ◽  
Import Receptor

scholarly journals Inactivation of the Neurospora crassa gene encoding the mitochondrial protein import receptor MOM19 by the technique of "sheltered RIP".

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 107-118 ◽  
Author(s):  
T A Harkness ◽  
R L Metzenberg ◽  
H Schneider ◽  
R Lill ◽  
W Neupert ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Target Gene ◽  
Protein Import ◽  
Selectable Marker ◽  
Mitochondrial Protein ◽  
Mutant Gene ◽  
Mitochondrial Protein Import ◽  
Gene Encoding ◽  
Precursor Proteins ◽  
Import Receptor

Abstract We have used a technique referred to as "sheltered RIP" (repeat induced point mutation) to create mutants of the mom-19 gene of Neurospora crassa, which encodes an import receptor for nuclear encoded mitochondrial precursor proteins. Sheltered RIP permits the isolation of a mutant gene in one nucleus, even if that gene is essential for the survival of the organism, by sheltering the nucleus carrying the mutant gene in a heterokaryon with an unaffected nucleus. Furthermore, the nucleus harboring the RIPed gene contains a selectable marker so that it is possible to shift nuclear ratios in the heterokaryons to a state in which the nucleus containing the RIPed gene predominates in cultures grown under selective conditions. This results in a condition where the target gene product should be present at very suboptimal levels and allows the study of the mutant phenotype. One allele of mom-19 generated by this method contains 44 transitions resulting in 18 amino acid substitutions. When the heterokaryon containing this allele was grown under conditions favoring the RIPed nucleus, no MOM19 protein was detectable in the mitochondria of the strain. Homokaryotic strains containing the RIPed allele exhibit a complex and extremely slow growth phenotype suggesting that the product of the mom-19 gene is important in N. crassa.

scholarly journals The Chloroplast Import Receptor Toc90 Partially Restores the Accumulation of Toc159 Client Proteins in the Arabidopsis thaliana ppi2 Mutant

2011 ◽  
Vol 4 (2) ◽  
pp. 252-263 ◽  
Author(s):  
Sibylle Infanger ◽  
Sylvain Bischof ◽  
Andreas Hiltbrunner ◽  
Birgit Agne ◽  
Sacha Baginsky ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chloroplast Import ◽  
Client Proteins ◽  
Import Receptor

scholarly journals The Chloroplast Import Receptor Toc34 Functions as Preprotein-Regulated GTPase

2002 ◽  
Vol 383 (12) ◽  
Author(s):  
M. Jelic ◽  
N. Sveshnikova ◽  
M. Motzkus ◽  
P. Hörth ◽  
J. Soll ◽  
...  
Keyword(s):  
Chloroplast Import ◽  
Import Receptor

scholarly journals Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membrane

2002 ◽  
Vol 159 (5) ◽  
pp. 845-854 ◽  
Author(s):  
Jörg Bauer ◽  
Andreas Hiltbrunner ◽  
Petra Weibel ◽  
Pierre-Alexandre Vidi ◽  
Mayte Alvarez-Huerta ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Essential Role ◽  
Protein Import ◽  
Chloroplast Envelope ◽  
Chloroplast Biogenesis ◽  
Gtp Binding ◽  
Precursor Proteins ◽  
Albino Mutant ◽  
Import Receptor

Two homologous GTP-binding proteins, atToc33 and atToc159, control access of cytosolic precursor proteins to the chloroplast. atToc33 is a constitutive outer chloroplast membrane protein, whereas the precursor receptor atToc159 also exists in a soluble, cytosolic form. This suggests that atToc159 may be able to switch between a soluble and an integral membrane form. By transient expression of GFP fusion proteins, mutant analysis, and biochemical experimentation, we demonstrate that the GTP-binding domain regulates the targeting of cytosolic atToc159 to the chloroplast and mediates the switch between cytosolic and integral membrane forms. Mutant atToc159, unable to bind GTP, does not reinstate a green phenotype in an albino mutant (ppi2) lacking endogenous atToc159, remaining trapped in the cytosol. Thus, the function of atToc159 in chloroplast biogenesis is dependent on an intrinsic GTP-regulated switch that controls localization of the receptor to the chloroplast envelope.

scholarly journals Modifications at the A-domain of the chloroplast import receptor Toc159

2010 ◽  
Vol 5 (11) ◽  
pp. 1513-1516 ◽  
Author(s):  
Birgit Agne ◽  
Felix Kessler
Keyword(s):  
Chloroplast Import ◽  
Import Receptor

scholarly journals Global kinome profiling reveals DYRK1A as critical activator of the human mitochondrial import machinery

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Corvin Walter ◽  
Adinarayana Marada ◽  
Tamara Suhm ◽  
Ralf Ernsberger ◽  
Vera Muders ◽  
...  
Keyword(s):  
Critical Role ◽  
Transcriptional Response ◽  
Autism Spectrum ◽  
Mitochondrial Proteome ◽  
Mitochondrial Structure ◽  
Disease Mechanisms ◽  
Precursor Proteins ◽  
And Function ◽  
Import Receptor ◽  
The Ideal

AbstractThe translocase of the outer mitochondrial membrane TOM constitutes the organellar entry gate for nearly all precursor proteins synthesized on cytosolic ribosomes. Thus, TOM presents the ideal target to adjust the mitochondrial proteome upon changing cellular demands. Here, we identify that the import receptor TOM70 is targeted by the kinase DYRK1A and that this modification plays a critical role in the activation of the carrier import pathway. Phosphorylation of TOM70Ser91 by DYRK1A stimulates interaction of TOM70 with the core TOM translocase. This enables transfer of receptor-bound precursors to the translocation pore and initiates their import. Consequently, loss of TOM70Ser91 phosphorylation results in a strong decrease in import capacity of metabolite carriers. Inhibition of DYRK1A impairs mitochondrial structure and function and elicits a protective transcriptional response to maintain a functional import machinery. The DYRK1A-TOM70 axis will enable insights into disease mechanisms caused by dysfunctional DYRK1A, including autism spectrum disorder, microcephaly and Down syndrome.

scholarly journals Targeting of an abundant cytosolic form of the protein import receptor at Toc159 to the outer chloroplast membrane

2001 ◽  
Vol 154 (2) ◽  
pp. 309-316 ◽  
Author(s):  
Andreas Hiltbrunner ◽  
Jörg Bauer ◽  
Pierre-Alexandre Vidi ◽  
Sibylle Infanger ◽  
Petra Weibel ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Large Scale ◽  
Protein Import ◽  
Protein Translocation ◽  
Soluble Form ◽  
Chloroplast Biogenesis ◽  
Outer Envelope ◽  
Precursor Proteins ◽  
Outer Envelope Membrane ◽  
Import Receptor

Chloroplast biogenesis requires the large-scale import of cytosolically synthesized precursor proteins. A trimeric translocon (Toc complex) containing two homologous GTP-binding proteins (atToc33 and atToc159) and a channel protein (atToc75) facilitates protein translocation across the outer envelope membrane. The mechanisms governing function and assembly of the Toc complex are not yet understood. This study demonstrates that atToc159 and its pea orthologue exist in an abundant, previously unrecognized soluble form, and partition between cytosol-containing soluble fractions and the chloroplast outer membrane. We show that soluble atToc159 binds directly to the cytosolic domain of atToc33 in a homotypic interaction, contributing to the integration of atToc159 into the chloroplast outer membrane. The data suggest that the function of the Toc complex involves switching of atToc159 between a soluble and an integral membrane form.

scholarly journals The chloroplast import receptor is an integral membrane protein of chloroplast envelope contact sites.

1990 ◽  
Vol 111 (5) ◽  
pp. 1825-1838 ◽  
Author(s):  
D J Schnell ◽  
G Blobel ◽  
D Pain
Keyword(s):  
Membrane Protein ◽  
Protein Import ◽  
Integral Membrane Protein ◽  
Chloroplast Envelope ◽  
Bisphosphate Carboxylase ◽  
Chloroplast Import ◽  
Chloroplast Membrane ◽  
Phosphate Translocator ◽  
Triton X ◽  
Import Receptor

A chloroplast import receptor from pea, previously identified by antiidiotypic antibodies was purified and its primary structure deduced from its cDNA sequence. The protein is a 36-kD integral membrane protein (p36) with eight potential transmembrane segments. Fab prepared from monospecific anti-p36 IgG inhibits the import of the ribulose-1,5-bisphosphate carboxylase small subunit precursor (pS) by interfering with pS binding at the chloroplast surface. Anti-p36 IgGs are able to immunoprecipitate a Triton X-100 soluble p36-pS complex, suggesting a direct interaction between p36 and pS. This immunoprecipitation was specific as it was abolished by a pS synthetic transit peptide, consistent with the transit sequence receptor function of p36. Immunoelectron microscopy localized p36 to regions of the outer chloroplast membrane that are in close contact with the inner chloroplast membrane. Comparison of the deduced sequence of pea p36 to that of other known proteins indicates a striking homology to a protein from spinach chloroplasts that was previously suggested to be the triose phosphate-3-phosphoglycerate-phosphate translocator (phosphate translocator) (Flügge, U. I., K. Fischer, A. Gross, W. Sebald, F. Lottspeich, and C. Eckerskorn. 1989. EMBO (Eur. Mol. Biol. Organ.) J. 8:39-46). However, incubation of Triton X-100 solubilized chloroplast envelope material with hydroxylapatite indicated that p36 was quantitatively absorbed, whereas previous reports have shown that phosphate translocator activity does not bind to hydroxylapatite (Flügge, U. I., and H. W. Heldt. 1981. Biochim. Biophys. Acta. 638:296-304. These data, in addition to the topology and import inhibition data presented in this report support the assignment of p36 as a receptor for chloroplast protein import, and argue against the assignment of the spinach homologue of this protein as the chloroplast phosphate translocator.

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