scholarly journals Chloroplast Ribosomes Interact With the Insertase Alb3 in the Thylakoid Membrane

2021 ◽  
Vol 12 ◽  
Author(s):  
Bernd Ackermann ◽  
Beatrix Dünschede ◽  
Björn Pietzenuk ◽  
Bo Højen Justesen ◽  
Ute Krämer ◽  
...  
Keyword(s):  
Thylakoid Membrane ◽  
Molecular Mechanisms ◽  
Phylogenetic Analyses ◽  
Signal Recognition Particle ◽  
Ribosomal Subunit ◽  
Terminal Region ◽  
Hydrophobic Core ◽  
C Terminus ◽  
Terrestrial Life ◽  
Nascent Chain

Members of the Oxa1/YidC/Alb3 protein family are involved in the insertion, folding, and assembly of membrane proteins in mitochondria, bacteria, and chloroplasts. The thylakoid membrane protein Alb3 mediates the chloroplast signal recognition particle (cpSRP)-dependent posttranslational insertion of nuclear-encoded light harvesting chlorophyll a/b-binding proteins and participates in the biogenesis of plastid-encoded subunits of the photosynthetic complexes. These subunits are cotranslationally inserted into the thylakoid membrane, yet very little is known about the molecular mechanisms underlying docking of the ribosome-nascent chain complexes to the chloroplast SecY/Alb3 insertion machinery. Here, we show that nanodisc-embedded Alb3 interacts with ribosomes, while the homolog Alb4, also located in the thylakoid membrane, shows no ribosome binding. Alb3 contacts the ribosome with its C-terminal region and at least one additional binding site within its hydrophobic core region. Within the C-terminal region, two conserved motifs (motifs III and IV) are cooperatively required to enable the ribosome contact. Furthermore, our data suggest that the negatively charged C-terminus of the ribosomal subunit uL4c is involved in Alb3 binding. Phylogenetic analyses of uL4 demonstrate that this region newly evolved in the green lineage during the transition from aquatic to terrestrial life.

scholarly journals Structural Basis for the C-Terminal Domain of Mycobacterium tuberculosis Ribosome Maturation Factor RimM to Bind Ribosomal Protein S19

Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 597
Author(s):  
Haoran Zhang ◽  
Qiuxiang Zhou ◽  
Chenyun Guo ◽  
Liubin Feng ◽  
Huilin Wang ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Ribosomal Protein ◽  
Solution Structure ◽  
Molecular Mechanisms ◽  
Structural Model ◽  
Ribosomal Subunit ◽  
Structural Basis ◽  
Hydrophobic Core ◽  
Terminal Domain ◽  
Ribosomal Protein S19

Multidrug-resistant tuberculosis (TB) is a serious threat to public health, calling for the development of new anti-TB drugs. Chaperon protein RimM, involved in the assembly of ribosomal protein S19 into 30S ribosomal subunit during ribosome maturation, is a potential drug target for TB treatment. The C-terminal domain (CTD) of RimM is primarily responsible for binding S19. However, both the CTD structure of RimM from Mycobacterium tuberculosis (MtbRimMCTD) and the molecular mechanisms underlying MtbRimMCTD binding S19 remain elusive. Here, we report the solution structure, dynamics features of MtbRimMCTD, and its interaction with S19. MtbRimMCTD has a rigid hydrophobic core comprised of a relatively conservative six-strand β-barrel, tailed with a short α-helix and interspersed with flexible loops. Using several biophysical techniques including surface plasmon resonance (SPR) affinity assays, nuclear magnetic resonance (NMR) assays, and molecular docking, we established a structural model of the MtbRimMCTD–S19 complex and indicated that the β4-β5 loop and two nonconserved key residues (D105 and H129) significantly contributed to the unique pattern of MtbRimMCTD binding S19, which might be implicated in a form of orthogonality for species-dependent RimM–S19 interaction. Our study provides the structural basis for MtbRimMCTD binding S19 and is beneficial to the further exploration of MtbRimM as a potential target for the development of new anti-TB drugs.

scholarly journals Molecular mechanisms of somatostatin receptor trafficking

2011 ◽  
Vol 48 (1) ◽  
pp. R1-R12 ◽  
Author(s):  
Zsolt Csaba ◽  
Stéphane Peineau ◽  
Pascal Dournaud
Keyword(s):  
Molecular Mechanisms ◽  
Somatostatin Receptor ◽  
Cell Types ◽  
Exocrine Secretion ◽  
Receptor Subtypes ◽  
Hydrophobic Core ◽  
Somatostatin Receptor Subtypes ◽  
C Terminus

The neuropeptide somatostatin (SRIF) is an important modulator of neurotransmission in the central nervous system and acts as a potent inhibitor of hormone and exocrine secretion. In addition, SRIF regulates cell proliferation in normal and tumorous tissues. The six somatostatin receptor subtypes (sst1, sst2A, sst2B, sst3, sst4, and sst5), which belong to the G protein-coupled receptor (GPCR) family, share a common molecular topology: a hydrophobic core of seven transmembrane-spanning α-helices, three intracellular loops, three extracellular loops, an amino-terminus outside the cell, and a carboxyl-terminus inside the cell. For most of the GPCRs, intracytosolic sequences, and more particularly the C-terminus, are believed to interact with proteins that are mandatory for either exporting neosynthesized receptor, anchoring receptor at the plasma membrane, internalization, recycling, or degradation after ligand binding. Accordingly, most of the SRIF receptors can traffic not onlyin vitrowithin different cell types but alsoin vivo. A picture of the pathways and proteins involved in these processes is beginning to emerge.

scholarly journals Mechanical force effect on the two-state equilibrium of the hyaluronan-binding domain of CD44 in cell rolling

2015 ◽  
Vol 112 (22) ◽  
pp. 6991-6996 ◽  
Author(s):  
Takashi Suzuki ◽  
Miho Suzuki ◽  
Shinji Ogino ◽  
Ryo Umemoto ◽  
Noritaka Nishida ◽  
...  
Keyword(s):  
Shear Stress ◽  
Conformational Change ◽  
Mechanical Force ◽  
Binding Domain ◽  
Terminal Region ◽  
Hematopoietic Progenitor Cell ◽  
High Shear ◽  
Cell Rolling ◽  
High Affinity ◽  
C Terminus

CD44 is the receptor for hyaluronan (HA) and mediates cell rolling under fluid shear stress. The HA-binding domain (HABD) of CD44 interconverts between a low-affinity, ordered (O) state and a high-affinity, partially disordered (PD) state, by the conformational change of the C-terminal region, which is connected to the plasma membrane. To examine the role of tensile force on CD44-mediated rolling, we used a cell-free rolling system, in which recombinant HABDs were attached to beads through a C-terminal or N-terminal tag. We found that the rolling behavior was stabilized only at high shear stress, when the HABD was attached through the C-terminal tag. In contrast, no difference was observed for the beads coated with HABD mutants that constitutively adopt either the O state or the PD state. Steered molecular dynamics simulations suggested that the force from the C terminus disrupts the interaction between the C-terminal region and the core of the domain, thus providing structural insights into how the mechanical force triggers the allosteric O-to-PD transition. Based on these results, we propose that the force applied from the C terminus enhances the HABD–HA interactions by inducing the conformational change to the high-affinity PD transition more rapidly, thereby enabling CD44 to mediate lymphocyte trafficking and hematopoietic progenitor cell homing under high-shear conditions.

scholarly journals Palmitoylation of Sindbis Virus TF Protein Regulates Its Plasma Membrane Localization and Subsequent Incorporation into Virions

2016 ◽  
Vol 91 (3) ◽  
Author(s):  
Jolene Ramsey ◽  
Emily C. Renzi ◽  
Randy J. Arnold ◽  
Jonathan C. Trinidad ◽  
Suchetana Mukhopadhyay
Keyword(s):  
Plasma Membrane ◽  
Sindbis Virus ◽  
Molecular Mechanisms ◽  
Wild Type Virus ◽  
Membrane Localization ◽  
Clear Understanding ◽  
Wild Type ◽  
Plasma Membrane Localization ◽  
C Terminus ◽  
N Terminus

ABSTRACT Palmitoylation is a reversible, posttranslational modification that helps target proteins to cellular membranes. The alphavirus small membrane proteins 6K and TF have been reported to be palmitoylated and to positively regulate budding. 6K and TF are isoforms that are identical in their N termini but unique in their C termini due to a −1 ribosomal frameshift during translation. In this study, we used cysteine (Cys) mutants to test differential palmitoylation of the Sindbis virus 6K and TF proteins. We modularly mutated the five Cys residues in the identical N termini of 6K and TF, the four additional Cys residues in TF's unique C terminus, or all nine Cys residues in TF. Using these mutants, we determined that TF palmitoylation occurs primarily in the N terminus. In contrast, 6K is not palmitoylated, even on these shared residues. In the C-terminal Cys mutant, TF protein levels increase both in the cell and in the released virion compared to the wild type. In viruses with the N-terminal Cys residues mutated, TF is much less efficiently localized to the plasma membrane, and it is not incorporated into the virion. The three Cys mutants have minor defects in cell culture growth but a high incidence of abnormal particle morphologies compared to the wild-type virus as determined by transmission electron microscopy. We propose a model where the C terminus of TF modulates the palmitoylation of TF at the N terminus, and palmitoylated TF is preferentially trafficked to the plasma membrane for virus budding. IMPORTANCE Alphaviruses are a reemerging viral cause of arthritogenic disease. Recently, the small 6K and TF proteins of alphaviruses were shown to contribute to virulence in vivo. Nevertheless, a clear understanding of the molecular mechanisms by which either protein acts to promote virus infection is missing. The TF protein is a component of budded virions, and optimal levels of TF correlate positively with wild-type-like particle morphology. In this study, we show that the palmitoylation of TF regulates its localization to the plasma membrane, which is the site of alphavirus budding. Mutants in which TF is not palmitoylated display drastically reduced plasma membrane localization, which effectively prevents TF from participating in budding or being incorporated into virus particles. Investigation of the regulation of TF will aid current efforts in the alphavirus field searching for approaches to mitigate alphaviral disease in humans.

scholarly journals Deletion of the Actin-Associated Tropomyosin Tpm3 Leads to Reduced Cell Complexity in Cultured Hippocampal Neurons—New Insights into the Role of the C-Terminal Region of Tpm3.1

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 715
Author(s):  
Tamara Tomanić ◽  
Claire Martin ◽  
Holly Stefen ◽  
Esmeralda Parić ◽  
Peter Gunning ◽  
...  
Keyword(s):  
Amino Acid ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Growth Cones ◽  
Amino Acid Residues ◽  
Terminal Amino Acid ◽  
C Terminus ◽  
Primary Mouse ◽  
Terminal Amino

Tropomyosins (Tpms) have been described as master regulators of actin, with Tpm3 products shown to be involved in early developmental processes, and the Tpm3 isoform Tpm3.1 controlling changes in the size of neuronal growth cones and neurite growth. Here, we used primary mouse hippocampal neurons of C57/Bl6 wild type and Bl6Tpm3flox transgenic mice to carry out morphometric analyses in response to the absence of Tpm3 products, as well as to investigate the effect of C-terminal truncation on the ability of Tpm3.1 to modulate neuronal morphogenesis. We found that the knock-out of Tpm3 leads to decreased neurite length and complexity, and that the deletion of two amino acid residues at the C-terminus of Tpm3.1 leads to more detrimental changes in neurite morphology than the deletion of six amino acid residues. We also found that Tpm3.1 that lacks the 6 C-terminal amino acid residues does not associate with stress fibres, does not segregate to the tips of neurites, and does not impact the amount of the filamentous actin pool at the axonal growth cones, as opposed to Tpm3.1, which lacks the two C-terminal amino acid residues. Our study provides further insight into the role of both Tpm3 products and the C-terminus of Tpm3.1, and it forms the basis for future studies that aim to identify the molecular mechanisms underlying Tpm3.1 targeting to different subcellular compartments.

scholarly journals N-myristoylation determines dual targeting of mammalian NADH-cytochrome b(5) reductase to ER and mitochondrial outer membranes by a mechanism of kinetic partitioning

2005 ◽  
Vol 168 (5) ◽  
pp. 735-745 ◽  
Author(s):  
Sara Colombo ◽  
Renato Longhi ◽  
Stefano Alcaro ◽  
Francesco Ortuso ◽  
Teresa Sprocati ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Signal Recognition Particle ◽  
Phospholipid Bilayer ◽  
Mitochondrial Outer Membrane ◽  
Signal Recognition ◽  
Outer Membranes ◽  
Dual Targeting ◽  
Nascent Chain ◽  
Hydrophobic Amino Acids ◽  
Nadh Cytochrome

Mammalian NADH-cytochrome b(5) reductase (b5R) is an N-myristoylated protein that is dually targeted to ER and mitochondrial outer membranes. The N-linked myristate is not required for anchorage to membranes because a stretch of hydrophobic amino acids close to the NH2 terminus guarantees a tight interaction of the protein with the phospholipid bilayer. Instead, the fatty acid is required for targeting of b5R to mitochondria because a nonmyristoylated mutant is exclusively localized to the ER. Here, we have investigated the mechanism by which N-linked myristate affects b5R targeting. We find that myristoylation interferes with interaction of the nascent chain with signal recognition particle, so that a portion of the nascent chains escapes from cotranslational integration into the ER and can be post-translationally targeted to the mitochondrial outer membrane. Thus, competition between two cotranslational events, binding of signal recognition particle and modification by N-myristoylation, determines the site of translation and the localization of b5R.

A description of the second species of the genus Bleptus Eaton, 1885 (Ephemeroptera: Heptageniidae) from Japan, and phylogenetic relationships of two Bleptus mayflies inferred from mitochondrial and nuclear gene sequences

Zootaxa ◽  
2021 ◽  
Vol 4974 (2) ◽  
pp. 333-360
Author(s):  
KOJI TOJO ◽  
KEN MIYAIRI ◽  
YUTO KATO ◽  
AYANA SAKANO ◽  
TOMOYA SUZUKI
Keyword(s):  
Phylogenetic Analyses ◽  
Ribosomal Subunit ◽  
Nuclear Gene ◽  
Taxonomic Status ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Gene Sequences ◽  
Molecular Phylogenetic ◽  
Black Band ◽  
Relationship Of

A new mayfly species, Bleptus michinokuensis sp. nov. (Ephemeroptera: Heptageniidae) is described on the basis of specimens of male and female adults and mature nymphs collected at a seepage zone of a small freshwater branch of the ‘Tachiya-zawa-gawa’ River located amongst the northern foothills of Mt. Gassan (Shonai-machi Town, Yamagata Prefecture, Japan). This new Bleptus species is characterized by its clear fore and hind wings. That is, they neither exhibit the distinct black band on the fore wings, nor the characteristic darkened margins along the edges of both the fore and hind wings. Rather it has a blackish colored terminal half of its fore legs (i.e., tibial, tarsal and pretarsal segments). These features differ clearly when comparing them to the other known species, Bleptus fasciatus Eaton. The information and data describing the habitat and distribution range of this new species are also noted. We also examined and discussed the genetic relationship of two Bleptus mayflies to settle the taxonomic status, inferred from the partially sequenced cytochrome c oxidase subunit I (COI) and large mitochondrial ribosomal subunit (16S rRNA) genes, and also the nuclear internal transcribed spacer 2 (ITS2) gene sequences. Consequently, phenetic and molecular phylogenetic analyses agreed well in terms of clustering. 

scholarly journals The C Terminus of the Ribosomal-Associated Protein LrtA is an Intrinsically Disordered Oligomer

2018 ◽  
Vol 19 (12) ◽  
pp. 3902 ◽  
Author(s):  
José L. Neira ◽  
A. Marcela Giudici ◽  
Felipe Hornos ◽  
Arantxa Arbe ◽  
Bruno Rizzuti
Keyword(s):  
Computational Modelling ◽  
Terminal Region ◽  
Physiological Conditions ◽  
Intrinsically Disordered ◽  
Disordered Protein ◽  
C Terminus ◽  
Conformational Preferences ◽  
Self Association ◽  
Association Equilibrium ◽  
Post Stress

The 191-residue-long LrtA protein of Synechocystis sp. PCC 6803 is involved in post-stress survival and in stabilizing 70S ribosomal particles. It belongs to the hibernating promoting factor (HPF) family, intervening in protein synthesis. The protein consists of two domains: The N-terminal region (N-LrtA, residues 1101), which is common to all the members of the HPF, and seems to be well-folded; and the C-terminal region (C-LrtA, residues 102-191), which is hypothesized to be disordered. In this work, we studied the conformational preferences of isolated C-LrtA in solution. The protein was disordered, as shown by computational modelling, 1D-1H NMR, steady-state far- UV circular dichroism (CD) and chemical and thermal denaturations followed by fluorescence and far-UV CD. Moreover, at physiological conditions, as indicated by several biochemical and hydrodynamic techniques, isolated C-LrtA intervened in a self-association equilibrium, involving several oligomerization reactions. Thus, C-LrtA was an oligomeric disordered protein.

scholarly journals Dissociation of the Tubulin-sequestering and Microtubule Catastrophe-promoting Activities of Oncoprotein 18/Stathmin

1999 ◽  
Vol 10 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Bonnie Howell ◽  
Niklas Larsson ◽  
Martin Gullberg ◽  
Lynne Cassimeris
Keyword(s):  
Tight Binding ◽  
Terminal Region ◽  
Microtubule Assembly ◽  
Gtp Hydrolysis ◽  
Truncated Protein ◽  
C Terminus ◽  
Dependent Change ◽  
Tubulin Subunit ◽  
Oncoprotein 18

Oncoprotein 18/stathmin (Op18) has been identified recently as a protein that destabilizes microtubules, but the mechanism of destabilization is currently controversial. Based on in vitro microtubule assembly assays, evidence has been presented supporting conflicting destabilization models of either tubulin sequestration or promotion of microtubule catastrophes. We found that Op18 can destabilize microtubules by both of these mechanisms and that these activities can be dissociated by changing pH. At pH 6.8, Op18 slowed microtubule elongation and increased catastrophes at both plus and minus ends, consistent with a tubulin-sequestering activity. In contrast, at pH 7.5, Op18 promoted microtubule catastrophes, particularly at plus ends, with little effect on elongation rates at either microtubule end. Dissociation of tubulin-sequestering and catastrophe-promoting activities of Op18 was further demonstrated by analysis of truncated Op18 derivatives. Lack of a C-terminal region of Op18 (aa 100–147) resulted in a truncated protein that lost sequestering activity at pH 6.8 but retained catastrophe-promoting activity. In contrast, lack of an N-terminal region of Op18 (aa 5–25) resulted in a truncated protein that still sequestered tubulin at pH 6.8 but was unable to promote catastrophes at pH 7.5. At pH 6.8, both the full length and the N-terminal–truncated Op18 bound tubulin, whereas truncation at the C-terminus resulted in a pronounced decrease in tubulin binding. Based on these results, and a previous study documenting a pH-dependent change in binding affinity between Op18 and tubulin, it is likely that tubulin sequestering observed at lower pH resulted from the relatively tight interaction between Op18 and tubulin and that this tight binding requires the C-terminus of Op18; however, under conditions in which Op18 binds weakly to tubulin (pH 7.5), Op18 stimulated catastrophes without altering tubulin subunit association or dissociation rates, and Op18 did not depolymerize microtubules capped with guanylyl (α, β)-methylene diphosphonate–tubulin subunits. We hypothesize that weak binding between Op18 and tubulin results in free Op18, which is available to interact with microtubule ends and thereby promote catastrophes by a mechanism that likely involves GTP hydrolysis.

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