scholarly journals Propulsive nanomachines: the convergent evolution of archaella, flagella and cilia

2020 ◽  
Vol 44 (3) ◽  
pp. 253-304 ◽  
Author(s):  
Morgan Beeby ◽  
Josie L Ferreira ◽  
Patrick Tripp ◽  
Sonja-Verena Albers ◽  
David R Mitchell
Keyword(s):  
Molecular Evolution ◽  
Convergent Evolution ◽  
Secretion System ◽  
Motive Force ◽  
Molecular Machine ◽  
Sensory Structure ◽  
Swimming Motility ◽  
Assembly Mechanism ◽  
Domains Of Life ◽  
Structure Assembly

ABSTRACT Echoing the repeated convergent evolution of flight and vision in large eukaryotes, propulsive swimming motility has evolved independently in microbes in each of the three domains of life. Filamentous appendages – archaella in Archaea, flagella in Bacteria and cilia in Eukaryotes – wave, whip or rotate to propel microbes, overcoming diffusion and enabling colonization of new environments. The implementations of the three propulsive nanomachines are distinct, however: archaella and flagella rotate, while cilia beat or wave; flagella and cilia assemble at their tips, while archaella assemble at their base; archaella and cilia use ATP for motility, while flagella use ion-motive force. These underlying differences reflect the tinkering required to evolve a molecular machine, in which pre-existing machines in the appropriate contexts were iteratively co-opted for new functions and whose origins are reflected in their resultant mechanisms. Contemporary homologies suggest that archaella evolved from a non-rotary pilus, flagella from a non-rotary appendage or secretion system, and cilia from a passive sensory structure. Here, we review the structure, assembly, mechanism and homologies of the three distinct solutions as a foundation to better understand how propulsive nanomachines evolved three times independently and to highlight principles of molecular evolution.

scholarly journals Weaving of bacterial cellulose by the Bcs secretion systems

2021 ◽  
Author(s):  
Wiem Abidi ◽  
Lucía Torres-Sánchez ◽  
Axel Siroy ◽  
Petya Violinova Krasteva
Keyword(s):  
Bacterial Cellulose ◽  
Bacterial Species ◽  
Secretion System ◽  
Secretion Systems ◽  
Bacterial Signaling ◽  
Accessory Subunits ◽  
Domains Of Life ◽  
The 19Th Century ◽  
Structure Assembly ◽  
Review Current

Abstract Cellulose is the most abundant biological compound on Earth and while it is the predominant building constituent of plants, it is also a key extracellular matrix component in many diverse bacterial species. While bacterial cellulose was first described in the 19th century, it was not until this last decade that a string of structural works provided insights into how the cellulose synthase BcsA, assisted by its inner-membrane partner BcsB, senses c-di-GMP to simultaneously polymerize its substrate and extrude the nascent polysaccharide across the inner bacterial membrane. It is now established that bacterial cellulose can be produced by several distinct types of cellulose secretion systems and that in addition to BcsAB, they can feature multiple accessory subunits, often indispensable for polysaccharide production. Importantly, the last years mark significant progress in our understanding not only of cellulose polymerization per se, but also of the bigger picture of bacterial signaling, secretion system assembly, biofilm formation and host tissue colonization, as well as of structural and functional parallels of this dominant biosynthetic process between the bacterial and eukaryotic domains of life. Here we review current mechanistic knowledge on bacterial cellulose secretion with focus on the structure, assembly and cooperativity of Bcs secretion system components.

Two Decanuclear DyIIIxCoII10–x (x = 2, 4) Nanoclusters: Structure, Assembly Mechanism, and Magnetic Properties

2021 ◽  
Vol 60 (7) ◽  
pp. 4904-4914
Author(s):  
Shui Yu ◽  
Hai-Ling Wang ◽  
Zilu Chen ◽  
Hua-Hong Zou ◽  
Huancheng Hu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Assembly Mechanism ◽  
Structure Assembly

scholarly journals The T3SS of Shigella: Expression, Structure, Function, and Role in Vacuole Escape

2020 ◽  
Vol 8 (12) ◽  
pp. 1933
Author(s):  
Waad Bajunaid ◽  
Nathaline Haidar-Ahmad ◽  
Anwer Hasil Kottarampatel ◽  
France Ourida Manigat ◽  
Navoun Silué ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Virulence Genes ◽  
Secretion System ◽  
Host Cells ◽  
Bacterial Membranes ◽  
Protein Substrates ◽  
Regulatory Cascade ◽  
Shigella Spp ◽  
Structure Assembly ◽  
Cell Spread

Shigella spp. are one of the leading causes of infectious diarrheal diseases. They are Escherichia coli pathovars that are characterized by the harboring of a large plasmid that encodes most virulence genes, including a type III secretion system (T3SS). The archetypal element of the T3SS is the injectisome, a syringe-like nanomachine composed of approximately 20 proteins, spanning both bacterial membranes and the cell wall, and topped with a needle. Upon contact of the tip of the needle with the plasma membrane, the injectisome secretes its protein substrates into host cells. Some of these substrates act as translocators or effectors whose functions are key to the invasion of the cytosol and the cell-to-cell spread characterizing the lifestyle of Shigella spp. Here, we review the structure, assembly, function, and methods to measure the activity of the injectisome with a focus on Shigella, but complemented with data from other T3SS if required. We also present the regulatory cascade that controls the expression of T3SS genes in Shigella. Finally, we describe the function of translocators and effectors during cell-to-cell spread, particularly during escape from the vacuole, a key element of Shigella’s pathogenesis that has yet to reveal all of its secrets.

scholarly journals Widespread convergence in toxin resistance by predictable molecular evolution

2015 ◽  
Vol 112 (38) ◽  
pp. 11911-11916 ◽  
Author(s):  
Beata Ujvari ◽  
Nicholas R. Casewell ◽  
Kartik Sunagar ◽  
Kevin Arbuckle ◽  
Wolfgang Wüster ◽  
...  
Keyword(s):  
Molecular Evolution ◽  
Cardiac Glycoside ◽  
Convergent Evolution ◽  
Point Mutations ◽  
Sodium Potassium ◽  
Toxin Resistance ◽  
The Subject ◽  
Taxonomic Groups ◽  
Core Part ◽  
Insight Into

The question about whether evolution is unpredictable and stochastic or intermittently constrained along predictable pathways is the subject of a fundamental debate in biology, in which understanding convergent evolution plays a central role. At the molecular level, documented examples of convergence are rare and limited to occurring within specific taxonomic groups. Here we provide evidence of constrained convergent molecular evolution across the metazoan tree of life. We show that resistance to toxic cardiac glycosides produced by plants and bufonid toads is mediated by similar molecular changes to the sodium-potassium-pump (Na+/K+-ATPase) in insects, amphibians, reptiles, and mammals. In toad-feeding reptiles, resistance is conferred by two point mutations that have evolved convergently on four occasions, whereas evidence of a molecular reversal back to the susceptible state in varanid lizards migrating to toad-free areas suggests that toxin resistance is maladaptive in the absence of selection. Importantly, resistance in all taxa is mediated by replacements of 2 of the 12 amino acids comprising the Na+/K+-ATPase H1–H2 extracellular domain that constitutes a core part of the cardiac glycoside binding site. We provide mechanistic insight into the basis of resistance by showing that these alterations perturb the interaction between the cardiac glycoside bufalin and the Na+/K+-ATPase. Thus, similar selection pressures have resulted in convergent evolution of the same molecular solution across the breadth of the animal kingdom, demonstrating how a scarcity of possible solutions to a selective challenge can lead to highly predictable evolutionary responses.

Molecules and morphology in basidiomycete phylogeny

1995 ◽  
Vol 73 (S1) ◽  
pp. 684-692 ◽  
Author(s):  
D. J. McLaughlin ◽  
M. E. Berres ◽  
L. J. Szabo
Keyword(s):  
Molecular Evolution ◽  
Nucleotide Sequence ◽  
Ribosomal Rna ◽  
Convergent Evolution ◽  
Large Subunit ◽  
Cladistic Analysis ◽  
Morphological Characters ◽  
Molecular Data ◽  
Large Subunit Ribosomal Rna ◽  
Molecular Characters

To obtain an understanding of the relationships of the basidiomycetes, especially those with horizontally partitioned metabasidia, and of the evolution of structural characters, members of nine orders and an additional four genera of simple-septate fungi (Auriculariales sensu lato) were studied using cladistic analysis of light microscopic and ultrastructural characters. Comparisons were made with the nucleotide sequence from the 5′ end of the nuclear large subunit ribosomal RNA gene analyzed with several algorithms, including parsimony and maximum likelihood. Analyses of both morphological and molecular characters support similar phylogenetic conclusions, but polarization of some morphological characters was difficult without guidance from molecular data. The Uredinales are shown to be an advanced taxon arising from the simple-septate Auriculariales sensu lato, and some characters that they share with the ascomycetes result from convergent evolution. The simple-septate Auriculariales consists of more than one clade, and the related gasteroid Pachnocybe ferruginea possesses numerous derived light microscopic characters, including holobasidia. Key words: basidiomycetes, character evolution, cladistics, molecular evolution, phylogeny.

scholarly journals Chaperone mediated coupling of subunit availability to activation of flagellar Type III Secretion

2020 ◽  
Author(s):  
Owain J. Bryant ◽  
Betty Y-W. Chung ◽  
Gillian M. Fraser
Keyword(s):  
Cell Membrane ◽  
Electric Potential ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Proton Motive Force ◽  
Secretion System ◽  
Motive Force ◽  
Type Iii

AbstractBacterial flagellar subunits are exported across the cell membrane by the flagellar Type III Secretion System (fT3SS), powered by the proton motive force (pmf) and a specialized ATPase that enables the flagellar export gate to utilise the pmf electric potential (ΔΨ). Export gate activation is mediated by the ATPase stalk, FliJ, but how this process is regulated to prevent wasteful dissipation of pmf in the absence of subunit cargo is not known. Here, we show that FliJ activation of the export gate is regulated by flagellar export chaperones. FliJ binds unladen chaperones and, using novel chaperone variants specifically defective for FliJ binding, we show that disruption of this interaction attenuates motility and cognate subunit export. We demonstrate in vitro that chaperones and the FlhA export gate component compete for binding to FliJ, and show in vivo that unladen chaperones, which would be present in the cell when subunit levels are low, sequester FliJ to prevent activation of the export gate and attenuate subunit export. Our data indicate a mechanism whereby chaperones couple availability of subunit cargo to pmf-driven export by the fT3SS.

scholarly journals The molecular evolution of function in the CFTR chloride channel

2021 ◽  
Vol 153 (12) ◽  
Author(s):  
Daniel T. Infield ◽  
Kerry M. Strickland ◽  
Amit Gaggar ◽  
Nael A. McCarty
Keyword(s):  
Cystic Fibrosis ◽  
Molecular Evolution ◽  
Abc Transporter ◽  
Atp Binding ◽  
Critical Question ◽  
Transport Pathway ◽  
Channel Function ◽  
Domains Of Life ◽  
Bona Fide ◽  
Channel Interactions

The ATP-binding cassette (ABC) transporter superfamily includes many proteins of clinical relevance, with genes expressed in all domains of life. Although most members use the energy of ATP binding and hydrolysis to accomplish the active import or export of various substrates across membranes, the cystic fibrosis transmembrane conductance regulator (CFTR) is the only known animal ABC transporter that functions primarily as an ion channel. Defects in CFTR, which is closely related to ABCC subfamily members that bear function as bona fide transporters, underlie the lethal genetic disease cystic fibrosis. This article seeks to integrate structural, functional, and genomic data to begin to answer the critical question of how the function of CFTR evolved to exhibit regulated channel activity. We highlight several examples wherein preexisting features in ABCC transporters were functionally leveraged as is, or altered by molecular evolution, to ultimately support channel function. This includes features that may underlie (1) construction of an anionic channel pore from an anionic substrate transport pathway, (2) establishment and tuning of phosphoregulation, and (3) optimization of channel function by specialized ligand–channel interactions. We also discuss how divergence and conservation may help elucidate the pharmacology of important CFTR modulators.

scholarly journals Origins and Molecular Evolution of the NusG Paralog RfaH

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Bing Wang ◽  
Vadim M. Gumerov ◽  
Ekaterina P. Andrianova ◽  
Igor B. Zhulin ◽  
Irina Artsimovitch
Keyword(s):  
Transcription Factors ◽  
Molecular Evolution ◽  
Rna Polymerase ◽  
Housekeeping Genes ◽  
Content Type ◽  
Bacterial Phyla ◽  
Evolutionary Origins ◽  
Genes Encoding ◽  
Domains Of Life ◽  
Polymerase Binding

ABSTRACT The only universally conserved family of transcription factors comprises housekeeping regulators and their specialized paralogs, represented by well-studied NusG and RfaH. Despite their ubiquity, little information is available on the evolutionary origins, functions, and gene targets of the NusG family members. We built a hidden Markov model profile of RfaH and identified its homologs in sequenced genomes. While NusG is widespread among bacterial phyla and coresides with genes encoding RNA polymerase and ribosome in all except extremely reduced genomes, RfaH is mostly limited to Proteobacteria and lacks common gene neighbors. RfaH activates only a few xenogeneic operons that are otherwise silenced by NusG and Rho. Phylogenetic reconstructions reveal extensive duplications and horizontal transfer of rfaH genes, including those borne by plasmids, and the molecular evolution pathway of RfaH, from “early” exclusion of the Rho terminator and tightened RNA polymerase binding to “late” interactions with the ops DNA element and autoinhibition, which together define the RfaH regulon. Remarkably, NusG is not only ubiquitous in Bacteria but also common in plants, where it likely modulates the transcription of plastid genes. IMPORTANCE In all domains of life, NusG-like proteins make contacts similar to those of RNA polymerase and promote pause-free transcription yet may play different roles, defined by their divergent interactions with nucleic acids and accessory proteins, in the same cell. This duality is illustrated by Escherichia coli NusG and RfaH, which silence and activate xenogenes, respectively. We combined sequence analysis and recent functional and structural insights to envision the evolutionary transformation of NusG, a core regulator that we show is present in all cells using bacterial RNA polymerase, into a virulence factor, RfaH. Our results suggest a stepwise conversion of a NusG duplicate copy into a sequence-specific regulator which excludes NusG from its targets but does not compromise the regulation of housekeeping genes. We find that gene duplication and lateral transfer give rise to a surprising diversity within the only ubiquitous family of transcription factors.

Sign in / Sign up

Export Citation Format

Share Document