scholarly journals A bipartite chromatophore transit peptide and N-terminal processing of protein in the Paulinella chromatophore

2021 ◽  
Author(s):  
Linda Oberleitner ◽  
Andreas Perrar ◽  
Luis Macorano ◽  
Pitter F. Huesgen ◽  
Eva C. M. Nowack
Keyword(s):  
Early Stage ◽  
Transit Peptide ◽  
Proteolytic Processing ◽  
Terminal Sequence ◽  
Dynamic Regulation ◽  
Unknown Mechanism ◽  
Recent Origin ◽  
Targeting Signals ◽  
Envelope Membranes ◽  
Double Envelope

The cercozoan amoeba Paulinella chromatophora contains photosynthetic organelles - termed chromatophores - that evolved from a cyanobacterium ~100 million years ago, independently from plastids in plants and algae. Despite its more recent origin, at least one third of the chromatophore proteome consists of nucleus-encoded proteins that are imported by an unknown mechanism across the chromatophore double envelope membranes. Chromatophore-targeted proteins fall into two classes. Proteins exceeding 250 amino acids carry a conserved N-terminal sequence extension, termed the 'chromatophore transit peptide' (crTP), that is presumably involved in guiding these proteins into the chromatophore. Short imported proteins do not carry discernable targeting signals. To explore whether the import of protein is accompanied by their N-terminal processing, here we used a mass spectrometry-based approach to determine protein N-termini in Paulinella chromatophora and identified N-termini of 208 chromatophore-localized proteins. Our study revealed extensive N-terminal modifications by acetylation and proteolytic processing in both, the nucleus and chromatophore-encoded fraction of the chromatophore proteome. Mature N-termini of 37 crTP-carrying proteins were identified, of which 30 were cleaved in a common processing region. Our results imply that the crTP mediates trafficking through the Golgi, is bipartite and surprisingly only the N-terminal third ('part 1') becomes cleaved upon import, whereas the rest ('part 2') remains at the mature proteins. In contrast, short imported proteins remain largely unprocessed. Finally, this work sheds light on N-terminal processing of proteins encoded in an evolutionary-early-stage photosynthetic organelle and suggests host-derived post-translationally acting factors involved in dynamic regulation of the chromatophore-encoded chromatophore proteome.

Mechanism of protein import across the chloroplast envelope

2000 ◽  
Vol 28 (4) ◽  
pp. 485-491 ◽  
Author(s):  
K. Chen ◽  
X. Chen ◽  
D. J. Schnell
Keyword(s):  
Protein Import ◽  
Essential Elements ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Subunits ◽  
Targeting Signals ◽  
Outer Envelope Membrane ◽  
Envelope Membranes

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toe apparatus) and inner (Tic apparatus) envelope membranes.

scholarly journals Robust expression of LINE-1 retrotransposon encoded proteins in oral squamous cell carcinoma

2020 ◽  
Author(s):  
Koel Mukherjee ◽  
Debpali Sur ◽  
Abhijeet Singh ◽  
Sandhya Rai ◽  
Neeladrisingha Das ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
Oral Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Early Stage ◽  
Antibody Detection ◽  
Normal Brain ◽  
Unknown Mechanism ◽  
Stage Of Development ◽  
Amino Acid Stretch

AbstractRetrotransposons are sequences which transpose within genomes using RNA as an intermediate. Long INterpersed Element-1 (LINE1 or L1) is the only active retrotransposon occupying around 17% of the human genome with an estimated 500,000 copies. An active L1 encodes two proteins (L1ORF1p and L1ORF2p); both of which are critical in the process of retrotransposition. In-order to propagate to the nextgeneration, L1s remain active in germ tissues and at an early stage of development. Surprisingly, by some unknown mechanism, L1 also shows activity in certain parts of the normal brain and many cancers. L1 activity is generally determined by assaying L1ORF1p because of its high expression and availability of the antibody. However, due to its lowerexpression and the unavailability of a robust antibody, detection of L1ORF2p has been limited. L1ORF2p is the crucial protein in the process of retrotransposition as it provides endonuclease and reverse transcriptase (RT) activity. Here, we report a novel human L1ORF2p antibody generated using an 80-amino-acid stretch from the RT domain, which is highly conserved among different species. The antibody detects significant L1ORF2p expression in murine germ tissues and human oral squamous cell carcinoma (OSCC) samples. This particular cancer is prevalent in India due to excessive use of tobacco. Here, using our in-house antibodies against L1 proteins, we show that more than fifty percent of samples are positive for L1 proteins. Overall, we reported a novel L1ORF2p antibody that detects L1 activity in germ tissues and OSCC

LonP1 regulates mitochondrial network remodeling through the PINK1/Parkin pathway during myoblast differentiation

2020 ◽  
Vol 319 (6) ◽  
pp. C1020-C1028
Author(s):  
Shiyuan Huang ◽  
Xiaona Wang ◽  
Jiale Yu ◽  
Yu Tian ◽  
Chenkai Yang ◽  
...  
Keyword(s):  
Matrix Protein ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Myoblast Differentiation ◽  
Mitochondrial Depolarization ◽  
Mitofusin 2 ◽  
Dynamic Regulation ◽  
Ubiquitin Protein Ligase ◽  
Mitochondrial Remodeling ◽  
Mitochondrial Networks

Myoblast differentiation is a crucial process for myogenesis. Mitochondria function as an energy-providing machine that is critical to this process, and mitochondrial dysfunction can prevent myoblasts from fusing into myotubes. However, the molecular mechanisms underlying the dynamic regulation of mitochondrial networks remain poorly understood. In the present study, we found that the PTEN induced kinase 1 (PINK1)/Parkin (an E3 ubiquitin-protein ligase) pathway is activated at the early stage of myoblast differentiation. Moreover, downregulation of mitofusin 2 (Mfn2) and increased dynamin-related protein 1 (Drp1) resulted in loosely formed mitochondria during this period. Furthermore, selective knockdown of the mitochondrial matrix protein Lon peptidase-1 (LonP1) at the early stage of myoblast differentiation induced mitochondrial depolarization and suppressed the PINK1/Parkin pathway and reduced Mfn2 and Drp1 levels, which blocked mitochondrial remodeling and myoblast differentiation. Overall, these data demonstrate that LonP1 promotes myoblast differentiation by regulating PINK1/Parkin-mediated mitochondrial remodeling.

scholarly journals The essential yeast protein MIM44 (encoded by MPI1) is involved in an early step of preprotein translocation across the mitochondrial inner membrane.

1993 ◽  
Vol 13 (12) ◽  
pp. 7364-7371 ◽  
Author(s):  
J Blom ◽  
M Kübrich ◽  
J Rassow ◽  
W Voos ◽  
P J Dekker ◽  
...  
Keyword(s):  
Protein Import ◽  
Early Stage ◽  
Proteolytic Processing ◽  
Early Step ◽  
Direct Role ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Preprotein Translocation ◽  
In Transit

The essential yeast gene MPI1 encodes a mitochondrial membrane protein that is possibly involved in protein import into the organelle (A. C. Maarse, J. Blom, L. A. Grivell, and M. Meijer, EMBO J. 11:3619-3628, 1992). For this report, we determined the submitochondrial location of the MPI1 gene product and investigated whether it plays a direct role in the translocation of preproteins. By fractionation of mitochondria, the mature protein of 44 kDa was localized to the mitochondrial inner membrane and therefore termed MIM44. Import of the precursor of MIM44 required a membrane potential across the inner membrane and involved proteolytic processing of the precursor. A preprotein in transit across the mitochondrial membranes was cross-linked to MIM44, whereas preproteins arrested on the mitochondrial surface or fully imported proteins were not cross-linked. When preproteins were arrested at two distinct stages of translocation across the inner membrane, only preproteins at an early stage of translocation could be cross-linked to MIM44. Moreover, solubilized MIM44 was found to interact with in vitro-synthesized preproteins. We conclude that MIM44 is a component of the mitochondrial inner membrane import machinery and interacts with preproteins in an early step of translocation.

scholarly journals Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

2016 ◽  
Vol 113 (38) ◽  
pp. 10714-10719 ◽  
Author(s):  
Amélie A. Kelly ◽  
Barbara Kalisch ◽  
Georg Hölzl ◽  
Sandra Schulze ◽  
Juliane Thiele ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Lipid Transfer ◽  
Terminal Sequence ◽  
Outer Envelope ◽  
Outer Envelope Membrane ◽  
Envelope Reconstruction ◽  
Envelope Membranes

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.

scholarly journals Directing Trophic Divergence in Plant-Pathogen Interactions: Antagonistic Phytohormones With NO Doubt?

2020 ◽  
Vol 11 ◽  
Author(s):  
Shuanglong Huang ◽  
Xuehua Zhang ◽  
W. G. Dilantha Fernando
Keyword(s):  
Nitric Oxide ◽  
Host Defense ◽  
Plant Pathogen ◽  
Defense Response ◽  
Early Stage ◽  
Dynamic Regulation ◽  
Nitric Oxide Signaling ◽  
Host Defense Response ◽  
Almost All ◽  
Plant Pathogen Interactions

A fundamental process culminating in the mechanisms of plant-pathogen interactions is the regulation of trophic divergence into biotrophic, hemibiotrophic, and necrotrophic interactions. Plant hormones, of almost all types, play significant roles in this regulatory apparatus. In plant-pathogen interactions, two classical mechanisms underlying hormone-dependent trophic divergence are long recognized. While salicylic acid dominates in the execution of host defense response against biotrophic and early-stage hemibiotrophic pathogens, jasmonic acid, and ethylene are key players facilitating host defense response against necrotrophic and later-stage hemibiotrophic pathogens. Evidence increasingly suggests that trophic divergence appears to be modulated by more complex signaling networks. Acting antagonistically or agonistically, other hormones such as auxins, cytokinins, abscisic acid, gibberellins, brassinosteroids, and strigolactones, as well as nitric oxide, are emerging candidates in the regulation of trophic divergence. In this review, the latest advances in the dynamic regulation of trophic divergence are summarized, emphasizing common and contrasting hormonal and nitric oxide signaling strategies deployed in plant-pathogen interactions.

Were class C iron-containing superoxide dismutases of trypanosomatid parasites initially imported into a complex plastid? A hypothesis based on analyses of their N-terminal targeting signals

Parasitology ◽  
2008 ◽  
Vol 135 (9) ◽  
pp. 1101-1110 ◽  
Author(s):  
A. BODYŁ ◽  
P. MACKIEWICZ
Keyword(s):  
Signal Peptide ◽  
Transit Peptide ◽  
Duplication Event ◽  
Superoxide Dismutases ◽  
Gene Encoding ◽  
Transit Peptides ◽  
Plastid Proteins ◽  
Trypanosomatid Parasites ◽  
Evolutionary Step ◽  
Targeting Signals

SUMMARYTrypanosomatid parasites possess 2 distinct iron-containing superoxide dismutases (Fe-SODs) designated SODA and SODC, both of which are targeted to their mitochondria. In contrast to SODAs that carry typical mitochondrial transit peptides, SODCs have highly unusual mitochondrial targeting signals. Our analyses clearly show that these pre-sequences are bipartite possessing a signal peptide-like domain followed by a transit peptide-like domain. Consequently, they resemble N-terminal extensions of proteins targeted to multi-membrane plastids, suggesting that trypanosomatids once contained a eukaryotic alga-derived plastid. Further support for this hypothesis comes from striking similarities in length, hydropathy profile, and amino acid composition of SODC pre-sequences to those of Euglena and dinoflagellate plastid proteins. To account for these data, we propose that the Trypanosomatidae initially possessed a gene encoding a mitochondrial Fe-SOD with a classical mitochondrial transit peptide. Before or after plastid acquisition, a gene duplication event gave rise to SODA and SODC. In a subsequent evolutionary step a signal peptide was linked to SODC, enabling its import into the plastid. When the trypanosomatid plastid subsequently was lost, natural selection favoured adaptation of the SODC N-terminal signal as a mitochondrial transit peptide and re-targeting to the mitochondrion.

scholarly journals Dynamic regulation of small RNAome during the early stage of cardiac differentiation from pluripotent embryonic stem cells

Genomics Data ◽  
2017 ◽  
Vol 12 ◽  
pp. 136-145 ◽  
Author(s):  
Yue Li ◽  
An Zeng ◽  
Ge Li ◽  
Ya-Na Guan ◽  
Huang-Tian Yang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Early Stage ◽  
Embryonic Stem ◽  
Cardiac Differentiation ◽  
Dynamic Regulation

scholarly journals African Swine Fever Virus Protein p17 Is Essential for the Progression of Viral Membrane Precursors toward Icosahedral Intermediates

2010 ◽  
Vol 84 (15) ◽  
pp. 7484-7499 ◽  
Author(s):  
Cristina Suárez ◽  
Javier Gutiérrez-Berzal ◽  
Germán Andrés ◽  
María L. Salas ◽  
Javier M. Rodríguez
Keyword(s):  
Early Stage ◽  
African Swine Fever Virus ◽  
Transmembrane Protein ◽  
African Swine Fever ◽  
Integral Membrane Protein ◽  
Proteolytic Processing ◽  
Fever Virus ◽  
Morphological Evidence ◽  
Virus Protein

ABSTRACT The first morphological evidence of African swine fever virus (ASFV) assembly is the appearance of precursor viral membranes, thought to derive from the endoplasmic reticulum, within the assembly sites. We have shown previously that protein p54, a viral structural integral membrane protein, is essential for the generation of the viral precursor membranes. In this report, we study the role of protein p17, an abundant transmembrane protein localized at the viral internal envelope, in these processes. Using an inducible virus for this protein, we show that p17 is essential for virus viability and that its repression blocks the proteolytic processing of polyproteins pp220 and pp62. Electron microscopy analyses demonstrate that when the infection occurs under restrictive conditions, viral morphogenesis is blocked at an early stage, immediately posterior to the formation of the viral precursor membranes, indicating that protein p17 is required to allow their progression toward icosahedral particles. Thus, the absence of this protein leads to an accumulation of these precursors and to the delocalization of the major components of the capsid and core shell domains. The study of ultrathin serial sections from cells infected with BA71V or the inducible virus under permissive conditions revealed the presence of large helicoidal structures from which immature particles are produced, suggesting that these helicoidal structures represent a previously undetected viral intermediate.

Caspase-3 and caspase-7 but not caspase-6 cleave Gas2 in vitro: implications for microfilament reorganization during apoptosis

1999 ◽  
Vol 112 (23) ◽  
pp. 4475-4482 ◽  
Author(s):  
A. Sgorbissa ◽  
R. Benetti ◽  
S. Marzinotto ◽  
C. Schneider ◽  
C. Brancolini
Keyword(s):  
Caspase 3 ◽  
Early Stage ◽  
Proteolytic Processing ◽  
Caspase 7 ◽  
Microfilament System ◽  
Caspase 6 ◽  
Shape Changes ◽  
Mcf 7

Apoptosis is characterized by proteolysis of specific cellular proteins by a family of cystein proteases known as caspases. Gas2, a component of the microfilament system, is cleaved during apoptosis and the cleaved form specifically regulates microfilaments and cell shape changes. We now demonstrate that Gas2 is a substrate of caspase-3 but not of caspase-6. Proteolytic processing both in vitro and in vivo is dependent on aspartic residue 279. Gas2 cleavage was only partially impaired in apoptotic MCF-7 cells which lack caspase-3, thus indicating that different caspases can process Gas2 in vivo. In vitro Gas2 was processed, albeit with low affinity, by caspase-7 thus suggesting that this caspase could be responsible for the incomplete Gas2 processing observed in UV treated MCF-7 cells. In vivo proteolysis of Gas2 was detected at an early stage of the apoptotic process when the cells are still adherent on the substrate and it was coupled to the specific rearrangement of the microfilament characterizing cell death. Finally we also demonstrated that Gas2 in vitro binds to F-actin, but this interaction was unaffected by the caspase-3 dependent proteolytic processing.

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