scholarly journals Controlling minimal and maximal hook-length of the bacterial flagellum

2020 ◽  
Author(s):  
Alina Guse ◽  
Manfred Rohde ◽  
Marc Erhardt
Keyword(s):  
Protein Production ◽  
Control Mechanism ◽  
Underlying Mechanism ◽  
Minimal Length ◽  
Deletion Mutants ◽  
Hook Length ◽  
Bacterial Flagellum ◽  
Terminal Domain ◽  
Molecular Ruler ◽  
Measuring Tape

AbstractHook-length control is a central checkpoint during assembly of the bacterial flagellum. During hook growth, a 405 amino acids (aa) protein, FliK, is intermittently secreted and thought to function as a molecular measuring tape that, in Salmonella, controls hook-length to 55 nm ± 6 nm. The underlying mechanism involves interactions of both the α-helical, N-terminal domain of FliK (FliKN) with the hook and hook cap, and of its C-terminal domain with a component of the export apparatus. However, various deletion mutants of FliKN display uncontrolled hook-length, which is not consistent with a ruler mechanism. Here, we carried out an extensive deletion analysis of FliKN to investigate its contribution in the hook-length control mechanism. We identified FliKN mutants deleted for up to 80 aa that retained wildtype motility. However, the short FliK variants did not produce shorter hook-lengths as expected from a physical ruler. Rather, the minimal length of the hook depends on the level of hook protein production and secretion. Our results thus support a model in which FliK functions as a hook growth terminator protein that limits the maximal length of the hook, and not as a molecular ruler that physically measures hook-length.

scholarly journals Hook-length of the bacterial flagellum is optimized for maximal stability of the flagellar bundle

2018 ◽  
Author(s):  
Imke Spöring ◽  
Vincent A. Martinez ◽  
Christian Hotz ◽  
Jana Schwarz-Linek ◽  
Keara L. Grady ◽  
...  
Keyword(s):  
Basal Body ◽  
Swimming Speed ◽  
Self Assembly ◽  
Nanometer Scale ◽  
Hook Length ◽  
Optimal Length ◽  
Directed Movement ◽  
Bacterial Flagellum ◽  
Evolutionary Forces ◽  
Molecular Ruler

AbstractMost bacteria swim in liquid environments by rotating one or several flagella. The long external filament of the flagellum is connected to a membrane-embedded basal-body by a flexible universal joint, the hook, which allows the transmission of motor torque to the filament. The length of the hook is controlled on a nanometer-scale by a sophisticated molecular ruler mechanism. However, why its length is stringently controlled has remained elusive. We engineered and studied a diverse set of hook-length variants ofSalmonella enterica. Measurements of plate-assay motility, single-cell swimming speed and directional persistence in quasi 2D and population-averaged swimming speed and body angular velocity in 3D revealed that the motility performance is optimal around the wild type hook-length. We conclude that too short hooks may be too stiff to function as a junction and too long hooks may buckle and create instability in the flagellar bundle. Accordingly, peritrichously flagellated bacteria move most efficiently as the distance travelled per body rotation is maximal and body wobbling is minimized. Thus, our results suggest that the molecular ruler mechanism evolved to control flagellar hook growth to the optimal length consistent with efficient bundle formation. The hook-length control mechanism is therefore a prime example of how bacteria evolved elegant, but robust mechanisms to maximize their fitness under specific environmental constraints.Author summaryMany bacteria use flagella for directed movement in liquid environments. The flexible hook connects the membrane-embedded basal-body of the flagellum to the long, external filament. Flagellar function relies on self-assembly processes that define or self-limit the lengths of major parts. The length of the hook is precisely controlled on a nanometer-scale by a molecular ruler mechanism. However, the physiological benefit of tight hook-length control remains unclear. Here, we show that the molecular ruler mechanism evolved to control the optimal length of the flagellar hook, which is consistent with efficient motility performance. These results highlight the evolutionary forces that enable flagellated bacteria to optimize their fitness in diverse environments and might have important implications for the design of swimming micro-robots.

scholarly journals The role of the FliK molecular ruler in hook-length control inSalmonella enterica

2010 ◽  
Vol 75 (5) ◽  
pp. 1272-1284 ◽  
Author(s):  
Marc Erhardt ◽  
Takanori Hirano ◽  
Yichu Su ◽  
Koushik Paul ◽  
Daniel H. Wee ◽  
...  
Keyword(s):  
Hook Length ◽  
Molecular Ruler

Modulation of Na+/H+exchange activity by Cl−

2001 ◽  
Vol 281 (1) ◽  
pp. C133-C141 ◽  
Author(s):  
Orit Aharonovitz ◽  
András Kapus ◽  
Katalin Szászi ◽  
Natasha Coady-Osberg ◽  
Tim Jancelewicz ◽  
...  
Keyword(s):  
Cell Volume ◽  
Underlying Mechanism ◽  
Intrinsic Activity ◽  
Atp Content ◽  
Extracellular Medium ◽  
Optimal Activity ◽  
Terminal Domain ◽  
Normal Transport ◽  
The Individual ◽  
Exchange Activity

Na+/H+ exchanger (NHE) activity is exquisitely dependent on the intra- and extracellular concentrations of Na+ and H+. In addition, Cl− ions have been suggested to modulate NHE activity, but little is known about the underlying mechanism, and the Cl− sensitivity of the individual isoforms has not been established. To explore their Cl− sensitivity, types 1, 2, and 3 Na+/H+ exchangers (NHE1, NHE2, and NHE3) were heterologously expressed in antiport-deficient cells. Bilateral replacement of Cl− with nitrate or thiocyanate inhibited the activity of all isoforms. Cl− depletion did not affect cell volume or the cellular ATP content, which could have indirectly altered NHE activity. The number of plasmalemmal exchangers was unaffected by Cl− removal, implying that inhibition was due to a decrease in the intrinsic activity of individual exchangers. Analysis of truncated mutants of NHE1 revealed that the anion sensitivity resides, at least in part, in the COOH-terminal domain of the exchanger. Moreover, readdition of Cl− into the extracellular medium failed to restore normal transport, suggesting that intracellular Cl− is critical for activity. Thus interaction of intracellular Cl− with the COOH terminus of NHE1 or with an associated protein is essential for optimal activity.

scholarly journals TTK/hMps1 Mediates the p53-Dependent Postmitotic Checkpoint by Phosphorylating p53 at Thr18

2009 ◽  
Vol 29 (11) ◽  
pp. 2935-2944 ◽  
Author(s):  
Yi-Fu Huang ◽  
Margaret Dah-Tsyr Chang ◽  
Sheau-Yann Shieh
Keyword(s):  
Cell Division ◽  
Genome Stability ◽  
Spindle Checkpoint ◽  
Underlying Mechanism ◽  
Dependent Manner ◽  
Deficient Mutant ◽  
Present Evidence ◽  
Checkpoint Kinase ◽  
Terminal Domain

ABSTRACT Upon prolonged arrest in mitosis, cells undergo adaptation and exit mitosis without cell division. These tetraploid cells are either eliminated by apoptosis or arrested in the subsequent G1 phase in a spindle checkpoint- and p53-dependent manner. p53 has long been known to be activated by spindle poisons, such as nocodazole and Taxol, although the underlying mechanism remains elusive. Here we present evidence that stabilization and activation of p53 by spindle disruption requires the spindle checkpoint kinase TTK/hMps1. TTK/hMps1 phoshorylates the N-terminal domain of p53 at Thr18, and this phosphorylation disrupts the interaction with MDM2 and abrogates MDM2-mediated p53 ubiquitination. Phosphorylation at Thr18 enhances p53-dependent activation of not only p21 but also Lats2, two mediators of the postmitotic checkpoint. Furthermore, a phospho-mimicking substitution at Thr18 (T18D) is more competent than the phospho-deficient mutant (T18A) in rescuing the tetraploid checkpoint defect of p53-depleted cells. Our findings therefore provide a mechanism connecting the spindle checkpoint with p53 in the maintenance of genome stability.

scholarly journals Community control in cellular protein production: consequences for amino acid starvation

2015 ◽  
Vol 373 (2056) ◽  
pp. 20150107 ◽  
Author(s):  
Frank S. Heldt ◽  
Chris A. Brackley ◽  
Celso Grebogi ◽  
Marco Thiel
Keyword(s):  
Amino Acid ◽  
Protein Production ◽  
Control Mechanism ◽  
Supply And Demand ◽  
Mrna Translation ◽  
Cellular Protein ◽  
Amino Acid Starvation ◽  
Community Control ◽  
Trna Species ◽  
A Cell

Deprivation of essential nutrients can have stark consequences for many processes in a cell. We consider amino acid starvation, which can result in bottlenecks in mRNA translation when ribosomes stall due to lack of resources, i.e. tRNAs charged with the missing amino acid. Recent experiments also show less obvious effects such as increased charging of other (non-starved) tRNA species and selective charging of isoaccepting tRNAs. We present a mechanism which accounts for these observations and shows that production of some proteins can actually increase under starvation. One might assume that such responses could only be a result of sophisticated control pathways, but here we show that these effects can occur naturally due to changes in the supply and demand for different resources, and that control can be accomplished through selective use of rare codons. We develop a model for translation which includes the dynamics of the charging and use of aminoacylated tRNAs, explicitly taking into account the effect of specific codon sequences. This constitutes a new control mechanism in gene regulation which emerges at the community level, i.e. via resources used by all ribosomes.

scholarly journals FliG Subunit Arrangement in the Flagellar Rotor Probed by Targeted Cross-Linking

2005 ◽  
Vol 187 (16) ◽  
pp. 5640-5647 ◽  
Author(s):  
Bryan J. Lowder ◽  
Mark D. Duyvesteyn ◽  
David F. Blair
Keyword(s):  
High Yield ◽  
Cross Linking ◽  
Amino Acid Residues ◽  
Electron Microscopic ◽  
Bacterial Flagellum ◽  
Terminal Domain ◽  
Complex Protein ◽  
Microscopic Studies ◽  
Discrete Domains ◽  
Α Helix

ABSTRACT FliG is a component of the switch complex on the rotor of the bacterial flagellum. Each flagellar motor contains about 25 FliG molecules. The protein of Escherichia coli has 331 amino acid residues and comprises at least two discrete domains. A C-terminal domain of about 100 residues functions in rotation and includes charged residues that interact with the stator protein MotA. Other parts of the FliG protein are essential for flagellar assembly and interact with the MS ring protein FliF and the switch complex protein FliM. The crystal structure of the middle and C-terminal parts of FliG shows two globular domains joined by an α-helix and a short extended segment that contains two well-conserved glycine residues. Here, we describe targeted cross-linking studies of FliG that reveal features of its organization in the flagellum. Cys residues were introduced at various positions, singly or in pairs, and cross-linking by a maleimide or disulfide-inducing oxidant was examined. FliG molecules with pairs of Cys residues at certain positions in the middle domain formed disulfide-linked dimers and larger multimers with a high yield, showing that the middle domains of adjacent subunits are in fairly close proximity and putting constraints on the relative orientation of the domains. Certain proteins with single Cys replacements in the C-terminal domain formed dimers with moderate yields but not larger multimers. On the basis of the cross-linking results and the data available from mutational and electron microscopic studies, we propose a model for the organization of FliG subunits in the flagellum.

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