scholarly journals Central Region of Wheat UCP Acts as a Major Signal for Protein Transport to Mitochondria, but Both Distal Regions can also Drive a Protein Import to Mitochondria

2005 ◽  
Vol 55 (4) ◽  
pp. 447-452
Author(s):  
Seiji Murayama ◽  
Hirokazu Handa
Keyword(s):  
Central Region ◽  
Protein Transport ◽  
Protein Import

scholarly journals Control of protein trafficking by reversible masking of transport signals

2016 ◽  
Vol 27 (8) ◽  
pp. 1310-1319 ◽  
Author(s):  
Omer Abraham ◽  
Karnit Gotliv ◽  
Anna Parnis ◽  
Gaelle Boncompain ◽  
Franck Perez ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Trafficking ◽  
Protein Transport ◽  
Protein Import ◽  
Binding Peptide ◽  
Protein Traffic ◽  
Alternative Approach ◽  
Targeting Signal ◽  
Regulated Trafficking ◽  
Streptavidin Binding

Systems that allow the control of protein traffic between subcellular compartments have been valuable in elucidating trafficking mechanisms. Most current approaches rely on ligand or light-controlled dimerization, which results in either retardation or enhancement of the transport of a reporter. We developed an alternative approach for trafficking regulation that we term “controlled unmasking of targeting elements” (CUTE). Regulated trafficking is achieved by reversible masking of the signal that directs the reporter to its target organelle, relying on the streptavidin–biotin system. The targeting signal is generated within or immediately after a 38–amino acid streptavidin-binding peptide (SBP) that is appended to the reporter. The binding of coexpressed streptavidin to SBP causes signal masking, whereas addition of biotin causes complex dissociation and triggers protein transport to the target organelle. We demonstrate the application of this approach to the control of nuclear and peroxisomal protein import and the generation of biotin-dependent trafficking through the endocytic and COPI systems. By simultaneous masking of COPI and endocytic signals, we were able to generate a synthetic pathway for efficient transport of a reporter from the plasma membrane to the endoplasmic reticulum.

scholarly journals Identification of Protein Transport Complexes in the Chloroplastic Envelope Membranes via Chemical Cross-Linking

1997 ◽  
Vol 136 (5) ◽  
pp. 983-994 ◽  
Author(s):  
Mitsuru Akita ◽  
Erik Nielsen ◽  
Kenneth Keegstra
Keyword(s):  
Membrane Proteins ◽  
Protein Transport ◽  
Protein Import ◽  
Cross Linking ◽  
Envelope Membrane ◽  
Precursor Proteins ◽  
Intact Chloroplasts ◽  
Outer Envelope Membrane ◽  
Envelope Membranes ◽  
Chemical Cross Linking

Transport of cytoplasmically synthesized proteins into chloroplasts uses an import machinery present in the envelope membranes. To identify the components of this machinery and to begin to examine how these components interact during transport, chemical cross-linking was performed on intact chloroplasts containing precursor proteins trapped at a particular stage of transport by ATP limitation. Large crosslinked complexes were observed using three different reversible homobifunctional cross-linkers. Three outer envelope membrane proteins (OEP86, OEP75, and OEP34) and one inner envelope membrane protein (IEP110), previously reported to be involved in protein import, were identified as components of these complexes. In addition to these membrane proteins, a stromal member of the hsp100 family, ClpC, was also present in the complexes. We propose that ClpC functions as a molecular chaperone, cooperating with other components to accomplish the transport of precursor proteins into chloroplasts. We also propose that each envelope membrane contains distinct translocation complexes and that a portion of these interact to form contact sites even in the absence of precursor proteins.

scholarly journals Sequence analysis and protein interactions of Arabidopsis CIA2 and CIL proteins

2020 ◽  
Author(s):  
Chun-Yen Yang ◽  
Chih-Wen Sun
Keyword(s):  
Protein Interactions ◽  
Protein Transport ◽  
Protein Import ◽  
Leaf Shape ◽  
Homologous Proteins ◽  
Protein Fragments ◽  
Nuclear Localization Signals ◽  
Flowering Control ◽  
Reduced Rate ◽  
Pale Green

Abstract Background: A previous screening of Arabidopsis thaliana for mutants exhibiting dysfunctional chloroplast protein transport identified the chloroplast import apparatus ( cia ) gene. The cia2 mutant has a pale green phenotype and reduced rate of protein import into chloroplasts, but leaf shape and size are similar to wild-type plants of the same developmental stage. Microarray analysis showed that nuclear CIA2 protein enhances expression of the Toc75 , Toc33 , CPN10 and cpRPs genes, thereby up-regulating protein import and synthesis efficiency in chloroplasts. CIA2-like (CIL) shares 65% sequence identity to CIA2, suggesting that CIL and CIA2 are homologous proteins in Arabidopsis. Here, we further assess the protein interactions and sequence features of CIA2 and CIL. Results: Subcellular localizations of truncated CIA2 protein fragments in our onion transient assay demonstrate that CIA2 contains two nuclear localization signals (NLS) located at amino acids (aa) 62-65 and 291-308, whereas CIL has only one NLS at aa 47-50. We screened a yeast two-hybrid (Y2H) Arabidopsis cDNA library to search for putative CIA2-interacting proteins and identified 12 nuclear proteins, including itself, CIL, and flowering-control proteins (such as CO, NF-YB1, NF-YC1, NF-YC9 and ABI3). Additional Y2H experiments demonstrate that CIA2 and CIL mainly interact with flowering-control proteins via their N-termini, but preferentially form homo- or hetero-dimers through their C-termini. Moreover, sequence alignment showed that the N-terminal sequences of CIA2, CIL and NF-YA are highly conserved. Therefore, NF-YA in the NF-Y complex could be substituted by CIA2 or CIL. Conclusions: We show that Arabidopsis CIA2 and CIL can interact with CO and NF-Y complex, so not only may they contribute to regulate chloroplast function but also to modulate flower development.

Protein transport across the peroxisomal membrane

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Wolfgang Girzalsky ◽  
Harald W. Platta ◽  
Ralf Erdmann
Keyword(s):  
Protein Transport ◽  
Protein Import ◽  
Current Knowledge ◽  
Soluble Proteins ◽  
Matrix Proteins ◽  
Peroxisomal Membrane ◽  
Oligomeric Proteins ◽  
Peroxisomal Protein ◽  
Polypeptide Chains

AbstractThe maintenance of peroxisome function depends on the formation of the peroxisomal membrane and the subsequent import of both membrane and matrix proteins. Without exception, peroxisomal matrix proteins are nuclear encoded, synthesized on free ribosomes and subsequently imported post-translationally. In contrast to other translocation systems that transport unfolded polypeptide chains, the peroxisomal import apparatus can facilitate the transport of folded and oligomeric proteins across the peroxisomal membrane. The peroxisomal protein import is mediated by cycling receptors that shuttle between the cytosol and peroxisomal lumen and depends on ATP and ubiquitin. In this brief review, we will summarize our current knowledge on the import of soluble proteins into the peroxisomal matrix.

scholarly journals Import into and Degradation of Cytosolic Proteins by Isolated Yeast Vacuoles

1999 ◽  
Vol 10 (9) ◽  
pp. 2879-2889 ◽  
Author(s):  
Martin Horst ◽  
Erwin C. Knecht ◽  
Peter V. Schu
Keyword(s):  
Mammalian Cells ◽  
Protein Transport ◽  
Protein Import ◽  
Degradation Pathway ◽  
Specific Protein ◽  
Transport Pathway ◽  
Cytosolic Proteins ◽  
Hsp70 Family ◽  
Vacuolar Protein ◽  
Shock Proteins

In eukaryotic cells, both lysosomal and nonlysosomal pathways are involved in degradation of cytosolic proteins. The physiological condition of the cell often determines the degradation pathway of a specific protein. In this article, we show that cytosolic proteins can be taken up and degraded by isolated Saccharomyces cerevisiae vacuoles. After starvation of the cells, protein uptake increases. Uptake and degradation are temperature dependent and show biphasic kinetics. Vacuolar protein import is dependent on cytosolic heat shock proteins of the hsp70 family and on protease-sensitive component(s) on the outer surface of vacuoles. Degradation of the imported cytosolic proteins depends on a functional vacuolar ATPase. We show that the cytosolic isoform of yeast glyceraldehyde-3-phosphate dehydrogenase is degraded via this pathway. This import and degradation pathway is reminiscent of the protein transport pathway from the cytosol to lysosomes of mammalian cells.

Molecular interactions within the plant TOC complex

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Maik S. Sommer ◽  
Enrico Schleiff
Keyword(s):  
Molecular Interactions ◽  
Protein Transport ◽  
Protein Import ◽  
Current Knowledge ◽  
Transport Processes ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Molecules ◽  
Membrane Bound ◽  
Cellular Compartments

Abstract Protein transport, especially into different cellular compartments, is a highly coordinated and regulated process. The molecular machineries which carry out these transport processes are highly complex in structure, function, and regulation. In the case of chloroplasts, thousands of protein molecules have been estimated to be transported across the double-membrane bound envelope per minute. In this brief review, we summarize current knowledge about the molecular interplay during precursor protein import into chloroplasts, focusing on the initial events at the outer envelope.

scholarly journals A High-Resolution Luminescent Assay for Rapid and Continuous Monitoring of Protein Translocation Across Biological Membranes

2018 ◽  
Author(s):  
Gonçalo C. Pereira ◽  
William J. Allen ◽  
Daniel W. Watkins ◽  
Lisa Buddrus ◽  
Dylan Noone ◽  
...  
Keyword(s):  
Time Resolution ◽  
Protein Transport ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Major Step ◽  
Kinetics Parameters ◽  
Luminescent Assay

ABSTRACTProtein translocation is a fundamental process in biology. Major gaps in our understanding of this process arises due the poor sensitivity, low time-resolution and irreproducibility of translocation assays. To address this, we applied NanoLuc split-luciferase to produce a new strategy for measuring protein transport. The system reduces the timescale of data collection from days to minutes, and allows continuous acquisition with a time-resolution in the order of seconds – yielding kinetics parameters suitable for mechanistic elucidation and mathematical fitting. To demonstrate its versatility, we implemented and validated the assay in vitro and in vivo for the bacterial Sec system, and the mitochondrial protein import apparatus. Overall, this technology represents a major step forward, providing a powerful new tool for fundamental mechanistic enquiry of protein translocation and for inhibitor (drug) screening, with an intensity and rigour unattainable through classical methods.

Quality control of protein import into mitochondria

2021 ◽  
Vol 478 (16) ◽  
pp. 3125-3143
Author(s):  
Fabian den Brave ◽  
Jeannine Engelke ◽  
Thomas Becker
Keyword(s):  
Quality Control ◽  
Stress Responses ◽  
Protein Transport ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Control Mechanisms ◽  
Unfolded Proteins ◽  
Control Factors ◽  
Precursor Proteins ◽  
Cellular Stress Responses

Mitochondria import about 1000 proteins that are produced as precursors on cytosolic ribosomes. Defects in mitochondrial protein import result in the accumulation of non-imported precursor proteins and proteotoxic stress. The cell is equipped with different quality control mechanisms to monitor protein transport into mitochondria. First, molecular chaperones guide unfolded proteins to mitochondria and deliver non-imported proteins to proteasomal degradation. Second, quality control factors remove translocation stalled precursor proteins from protein translocases. Third, protein translocases monitor protein sorting to mitochondrial subcompartments. Fourth, AAA proteases of the mitochondrial subcompartments remove mislocalized or unassembled proteins. Finally, impaired efficiency of protein transport is an important sensor for mitochondrial dysfunction and causes the induction of cellular stress responses, which could eventually result in the removal of the defective mitochondria by mitophagy. In this review, we summarize our current understanding of quality control mechanisms that govern mitochondrial protein transport.

Regulation of protein transport to the nucleus: central role of phosphorylation

1996 ◽  
Vol 76 (3) ◽  
pp. 651-685 ◽  
Author(s):  
D. A. Jans ◽  
S. Hubner
Keyword(s):  
Nuclear Localization ◽  
Protein Transport ◽  
Protein Import ◽  
Nuclear Protein ◽  
Nuclear Transport ◽  
Simian Virus 40 ◽  
Nuclear Accumulation ◽  
Control Of Gene Expression ◽  
Nuclear Localization Signals

Nuclear protein transport is integral to eukaryotic cell processes such as differentiation, transformation, and the control of gene expression. Although the targeting role of nuclear localization signals (NLSs) has been known for some time, more recent results indicate that NLS-dependent nuclear protein import is precisely regulated. Phosphorylation appears to be the main mechanism controlling the nuclear transport of a number of proteins, including transcription factors such as NFkappaB, c-rel, dorsal, and SWI5 from yeast. Cytoplasmic retention factors, intra- and intermolecular NLS masking, and NLS masking by phosphorylation are some of the mechanisms by which phosphorylation specifically regulates nuclear transport. Even nuclear localization of the archetypal NLS-containing simian virus 40 large tumor antigen (T-ag) is regulated, namely by the "CcN motif," which comprises the T-ag NLS ("N") determining ultimate subcellular destination, a casein kinase II site ("C") 13 amino acids NH2-terminal to the NLS modulating the rate of nuclear import, and a cyclin-dependent kinase site ("c") adjacent to the NLS regulating the maximal level of nuclear accumulation. The CcN motif appears to be a special form of phosphorylation-regulated NLS (prNLS), where phosphorylation at site(s) close to the NLS specifically regulates NLS function. The regulation of nuclear transport through phosphorylation and prNLSs appears to be common in eukaryotic cells from yeast and plants to higher mammals.

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