scholarly journals Differences in structure and hibernation mechanism highlight diversification of the microsporidian ribosome

PLoS Biology ◽  
2020 ◽  
Vol 18 (10) ◽  
pp. e3000958
Author(s):  
Kai Ehrenbolger ◽  
Nathan Jespersen ◽  
Himanshu Sharma ◽  
Yuliya Y. Sokolova ◽  
Yuri S. Tokarev ◽  
...  
Keyword(s):  
Large Subunit ◽  
Control Mechanisms ◽  
Emerging Pathogens ◽  
Conservation Of Energy ◽  
Nutrient Limitations ◽  
Cryo Electron Microscopy ◽  
Inactivation Mechanism ◽  
Ribosome Inactivation ◽  
Cellular Control ◽  
Trna Binding

Assembling and powering ribosomes are energy-intensive processes requiring fine-tuned cellular control mechanisms. In organisms operating under strict nutrient limitations, such as pathogenic microsporidia, conservation of energy via ribosomal hibernation and recycling is critical. The mechanisms by which hibernation is achieved in microsporidia, however, remain poorly understood. Here, we present the cryo–electron microscopy structure of the ribosome from Paranosema locustae spores, bound by the conserved eukaryotic hibernation and recycling factor Lso2. The microsporidian Lso2 homolog adopts a V-shaped conformation to bridge the mRNA decoding site and the large subunit tRNA binding sites, providing a reversible ribosome inactivation mechanism. Although microsporidian ribosomes are highly compacted, the P. locustae ribosome retains several rRNA segments absent in other microsporidia, and represents an intermediate state of rRNA reduction. In one case, the near complete reduction of an expansion segment has resulted in a single bound nucleotide, which may act as an architectural co-factor to stabilize a protein–protein interface. The presented structure highlights the reductive evolution in these emerging pathogens and sheds light on a conserved mechanism for eukaryotic ribosome hibernation.

scholarly journals Differences in structure and hibernation mechanism highlight diversification of the microsporidian ribosome

2020 ◽  
Author(s):  
Kai Ehrenbolger ◽  
Nathan Jespersen ◽  
Himanshu Sharma ◽  
Yuliya Y. Sokolova ◽  
Yuri S. Tokarev ◽  
...  
Keyword(s):  
Binding Sites ◽  
Large Subunit ◽  
Control Mechanisms ◽  
Emerging Pathogens ◽  
Conservation Of Energy ◽  
Nutrient Limitations ◽  
Inactivation Mechanism ◽  
Ribosome Inactivation ◽  
Cellular Control ◽  
Trna Binding

AbstractAssembling and powering ribosomes are energy-intensive processes requiring fine-tuned cellular control mechanisms. In organisms operating under strict nutrient limitations, such as pathogenic microsporidia, conservation of energy via ribosomal hibernation and recycling is critical. The mechanisms by which hibernation is achieved in microsporidia, however, remain poorly understood. Here, we present the cryo-EM structure of the ribosome from Paranosema locustae spores, bound by the conserved eukaryotic hibernation and recycling factor Lso2. The microsporidian Lso2 homolog adopts a V-shaped conformation to bridge the mRNA decoding site and the large subunit tRNA binding sites, providing a reversible ribosome inactivation mechanism. Although microsporidian ribosomes are universally highly compacted, the P. locustae ribosome retains several rRNA segments absent in other microsporidia, and represents an intermediate state of rRNA reduction. In one case, the near complete reduction of an expansion segment has resulted in a single bound nucleotide, which acts as an architectural co-factor to stabilize a protein-protein interface. The presented structure highlights the reductive evolution in these emerging pathogens and sheds light on a conserved mechanism for eukaryotic ribosome hibernation.

scholarly journals Structural consequences of the interaction of RbgA with a 50S ribosomal subunit assembly intermediate

2019 ◽  
Vol 47 (19) ◽  
pp. 10414-10425 ◽  
Author(s):  
Amal Seffouh ◽  
Nikhil Jain ◽  
Dushyant Jahagirdar ◽  
Kaustuv Basu ◽  
Aida Razi ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Large Subunit ◽  
Ribosomal Subunit ◽  
Catalytic Residue ◽  
Gtp Hydrolysis ◽  
Subunit Assembly ◽  
Cryo Electron Microscopy ◽  
Assembly Factor ◽  
Assembly Intermediate ◽  
Immature Particle

Abstract Bacteria harbor a number GTPases that function in the assembly of the ribosome and are essential for growth. RbgA is one of these GTPases and is required for the assembly of the 50S subunit in most bacteria. Homologs of this protein are also implicated in the assembly of the large subunit of the mitochondrial and eukaryotic ribosome. We present here the cryo-electron microscopy structure of RbgA bound to a Bacillus subtilis 50S subunit assembly intermediate (45SRbgA particle) that accumulates in cells upon RbgA depletion. Binding of RbgA at the P site of the immature particle stabilizes functionally important rRNA helices in the A and P-sites, prior to the completion of the maturation process of the subunit. The structure also reveals the location of the highly conserved N-terminal end of RbgA containing the catalytic residue Histidine 9. The derived model supports a mechanism of GTP hydrolysis, and it shows that upon interaction of RbgA with the 45SRbgA particle, Histidine 9 positions itself near the nucleotide potentially acting as the catalytic residue with minimal rearrangements. This structure represents the first visualization of the conformational changes induced by an assembly factor in a bacterial subunit intermediate.

scholarly journals Functional domains of the 50S subunit mature late in the assembly process

2013 ◽  
Vol 42 (5) ◽  
pp. 3419-3435 ◽  
Author(s):  
Ahmad Jomaa ◽  
Nikhil Jain ◽  
Joseph H. Davis ◽  
James R. Williamson ◽  
Robert A. Britton ◽  
...  
Keyword(s):  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Molecular Mechanisms ◽  
Functional Sites ◽  
Chemical Probing ◽  
Cryo Electron Microscopy ◽  
Mass Spectrometry Technique ◽  
Spectrometry Technique ◽  
Late Stages ◽  
Trna Binding

Abstract Despite the identification of many factors that facilitate ribosome assembly, the molecular mechanisms by which they drive ribosome biogenesis are poorly understood. Here, we analyze the late stages of assembly of the 50S subunit using Bacillus subtilis cells depleted of RbgA, a highly conserved GTPase. We found that RbgA-depleted cells accumulate late assembly intermediates bearing sub-stoichiometric quantities of ribosomal proteins L16, L27, L28, L33a, L35 and L36. Using a novel pulse labeling/quantitative mass spectrometry technique, we show that this particle is physiologically relevant and is capable of maturing into a complete 50S particle. Cryo-electron microscopy and chemical probing revealed that the central protuberance, the GTPase associating region and tRNA-binding sites in this intermediate are unstructured. These findings demonstrate that key functional sites of the 50S subunit remain unstructured until late stages of maturation, preventing the incomplete subunit from prematurely engaging in translation. Finally, structural and biochemical analysis of a ribosome particle depleted of L16 indicate that L16 binding is necessary for the stimulation of RbgA GTPase activity and, in turn, release of this co-factor, and for conversion of the intermediate to a complete 50S subunit.

Cellular Control Mechanisms and Cancer.

1965 ◽  
Vol 62 (1) ◽  
pp. 179
Keyword(s):  
Control Mechanisms ◽  
Cellular Control

Effects of Drugs on Cellular Control Mechanisms.

1973 ◽  
Vol 78 (2) ◽  
pp. 329
Keyword(s):  
Control Mechanisms ◽  
Cellular Control

scholarly journals Gastrin activates paracrine networks leading to induction of PAI-2 via MAZ and ASC-1

2009 ◽  
Vol 296 (2) ◽  
pp. G414-G423 ◽  
Author(s):  
Simon Almeida-Vega ◽  
Krista Catlow ◽  
Susan Kenny ◽  
Rod Dimaline ◽  
Andrea Varro
Keyword(s):  
Plasminogen Activator ◽  
Mutational Analysis ◽  
Plasminogen Activator Inhibitor ◽  
Small Gtpase ◽  
Control Mechanisms ◽  
Site Mutation ◽  
Tissue Responses ◽  
Cellular Control ◽  
Activator Inhibitor ◽  
Hybrid Screening

The gastric hormone gastrin regulates the expression of a variety of genes involved in control of acid secretion and also in the growth and organization of the gastric mucosa. One putative target is plasminogen activator inhibitor-2 (PAI-2), which is a component of the urokinase activator system that acts extracellularly to inhibit urokinase plasminogen activator (uPA) and intracellularly to suppress apoptosis. Previous studies have demonstrated that gastrin induces PAI-2 both in gastric epithelial cells expressing the gastrin (CCK-2) receptor and, via activation of paracrine networks, in adjacent cells that do not express the receptor. We have now sought to identify the response element(s) in the PAI-2 promoter targeted by paracrine mediators initiated by gastrin. Mutational analysis identified two putative response elements in the PAI-2 promoter that were downstream of gastrin-activated paracrine signals. One was identified as a putative MAZ site, mutation of which dramatically reduced both basal and gastrin-stimulated responses of the PAI-2 promoter by a mechanism involving PGE2 and the small GTPase RhoA. Yeast one-hybrid screening identified the other as binding the activating signal cointegrator-1 (ASC-1) complex, which was shown to be the target of IL-8 released by gastrin. RNA interference (RNAi) knockdown of two subunits of the ASC-1 complex (p50 and p65) inhibited induction of PAI-2 expression by gastrin. The data reveal previously unsuspected transcriptional mechanisms activated as a consequence of gastrin-triggered paracrine networks and emphasize the elaborate and complex cellular control mechanisms required for a key component of tissue responses to damage and infection.

Sign in / Sign up

Export Citation Format

Share Document