scholarly journals Roles of Titin in the Structure and Elasticity of the Sarcomere

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Larissa Tskhovrebova ◽  
John Trinick
Keyword(s):  
Elastic Properties ◽  
Operating Range ◽  
Titin Molecule ◽  
Thick Filaments ◽  
Structural Details ◽  
And Function ◽  
Rest Length

The giant protein titin is thought to play major roles in the assembly and function of muscle sarcomeres. Structural details, such as widths of Z- and M-lines and periodicities in the thick filaments, correlate with the substructure in the respective regions of the titin molecule. Sarcomere rest length, its operating range of lengths, and passive elastic properties are also directly controlled by the properties of titin. Here we review some recent titin data and discuss its implications for sarcomere architecture and elasticity.

scholarly journals Identification and functional characterization of the Piezo1 channel pore domain

2020 ◽  
pp. jbc.RA120.015905
Author(s):  
Elena D Nosyreva ◽  
David Thompson ◽  
Ruhma Syeda
Keyword(s):  
Functional Characterization ◽  
Functional Study ◽  
Heat Sensation ◽  
Physiological Processes ◽  
Structural Details ◽  
Functional Understanding ◽  
And Function ◽  
Downstream Processes ◽  
Pore Domain ◽  
First Time

Mechanotransduction is the process by which cells convert physical forces into electro-chemical responses. On a molecular scale these forces are detected by mechanically activated ion channels, which constitute the basis for hearing, touch, pain, cold and heat sensation amongst other physiological processes. Exciting high-resolution structural details of these channels are currently emerging that will eventually allow us to delineate the molecular determinants of gating and ion permeation. However, our structural-functional understanding across the family remains limited. Piezo1 is one of the largest and least understood of these channels, with various structurally identified features within its trimeric assembly. This study seeks to determine the modularity and function of Piezo1 channels by constructing deletion proteins guided by cryo EM structural knowledge. Our comprehensive functional study identified, for the first time, the minimal amino acid sequence of the full-length Piezo1 that can fold and function as the channel’s pore domain between E2172 and the last residue E2547. While, the addition of an anchor region has no effect on permeation properties. The Piezo1 pore domain is not pressure sensitive and the appending of Piezo Repeat-A did not restore pressure-dependent gating, hence the sensing module must exist between residues 1-1952. Our efforts delineating the permeation and gating regions within this complex ion channel have implications in identifying small molecules that exclusively regulate the activity of the channel’s pore module to influence mechanotransduction and downstream processes.

scholarly journals Bacterial flagellar motor

2008 ◽  
Vol 41 (2) ◽  
pp. 103-132 ◽  
Author(s):  
Yoshiyuki Sowa ◽  
Richard M. Berry
Keyword(s):  
Single Molecule ◽  
Cell Envelope ◽  
Molecular Motor ◽  
Motive Force ◽  
Flagellar Motor ◽  
Large Size ◽  
Structural Details ◽  
Bacterial Flagellar Motor ◽  
And Function ◽  
Rotary Motor

AbstractThe bacterial flagellar motor is a reversible rotary nano-machine, about 45 nm in diameter, embedded in the bacterial cell envelope. It is powered by the flux of H+or Na+ions across the cytoplasmic membrane driven by an electrochemical gradient, the proton-motive force or the sodium-motive force. Each motor rotates a helical filament at several hundreds of revolutions per second (hertz). In many species, the motor switches direction stochastically, with the switching rates controlled by a network of sensory and signalling proteins. The bacterial flagellar motor was confirmed as a rotary motor in the early 1970s, the first direct observation of the function of a single molecular motor. However, because of the large size and complexity of the motor, much remains to be discovered, in particular, the structural details of the torque-generating mechanism. This review outlines what has been learned about the structure and function of the motor using a combination of genetics, single-molecule and biophysical techniques, with a focus on recent results and single-molecule techniques.

Structure and function of the important internalins of Listeria monocytogenes

2021 ◽  
Vol 22 ◽  
Author(s):  
Shabir Ahmad Mir
Keyword(s):  
Listeria Monocytogenes ◽  
Virulence Factors ◽  
Causative Agent ◽  
Structure And Function ◽  
Intracellular Bacterium ◽  
Infection Cycle ◽  
Current Review ◽  
Functional Aspects ◽  
Structural Details ◽  
And Function

: Listeria monocytogenes, a facultative intracellular gram-positive pathogen, is the causative agent of the disease listeriosis. The virulence of this intracellular bacterium is dependent on the coordinated activity of various bacterial factors, which are in turn tightly controlled by a specific set of regulators. The arsenal of virulence factors employed by L. monocytogenes for its infection cycle is available in the literature. Although the internalins of L. monocytogenes have been studied in detail their structural details are currently scattered and fragmented. Therefore, in the current review, we provide a brief account of the existing knowledge on structural details of the key internalins of L. monocytogenes and also highlight the recent advances in their functional aspects.

scholarly journals MECHANISM OF SUPERCONTRACTION IN A STRIATED MUSCLE

1965 ◽  
Vol 26 (2) ◽  
pp. 621-640 ◽  
Author(s):  
Graham Hoyle ◽  
James H. McAlear ◽  
Allen Selverston
Keyword(s):  
Phase Contrast ◽  
Striated Muscle ◽  
Active Process ◽  
High Concentration ◽  
Thick Filaments ◽  
Pass Through ◽  
Contraction Band ◽  
Evoked Contractions ◽  
Opening Up ◽  
Rest Length

The phenomenon of contraction of a striated muscle down to below 50 per cent rest length has been examined for the scutal depressor of the barnacle Balanus nubilus by a combination of phase contrast and electron microscopy. It was found that neurally evoked contraction down to 60 per cent rest length results from the shortening of the I band. At the same time the Z disc changes in structure by an active process which results in spaces opening up within it. Thick filaments can now pass through these spaces from adjacent sarcomeres, interdigitating across the discs. Interdigitation permits repetitive contraction in the living muscle to below 30 per cent rest length. In non-neurally evoked contractions most thick filaments do not find spaces in the Z disc and bend back, giving rise to contraction band artifacts. Expansion of the Z disc can be produced in glycerinated material by the addition of solutions containing a high concentration of ATP.

Microbial siderophore-mediated transport

2002 ◽  
Vol 30 (4) ◽  
pp. 691-696 ◽  
Author(s):  
G. Winkelmann
Keyword(s):  
Transport Properties ◽  
Present Review ◽  
Iron Availability ◽  
Iron Chelates ◽  
Structural Details ◽  
Bacteria And Fungi ◽  
And Function

Microbial iron chelates, called siderophores, are synthesized by bacteria and fungi in response to low iron availability in the environment. The present review summarizes structural details of siderophore ligands with respect to their transport properties. This presentation is largely centred on the occurrence and function of siderophores in the various bacterial and fungal genera.

scholarly journals Elastic Properties of Isolated Thick Filaments Measured by Nanofabricated Cantilevers

1998 ◽  
Vol 75 (2) ◽  
pp. 938-947 ◽  
Author(s):  
Thomas Neumann ◽  
Mark Fauver ◽  
Gerald H. Pollack
Keyword(s):  
Elastic Properties ◽  
Thick Filaments

scholarly journals Generation of a Highly Biomimetic Organoid, Including Vasculature, Resembling the Native Immature Testis Tissue

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1696
Author(s):  
Tat-Chuan Cham ◽  
Fahar Ibtisham ◽  
Mohammad Amin Fayaz ◽  
Ali Honaramooz
Keyword(s):  
Culture System ◽  
Complex Form ◽  
Cell Types ◽  
Form And Function ◽  
Donor Cells ◽  
Structural Details ◽  
Vascular Structures ◽  
And Function ◽  
Air Liquid Interface ◽  
Testis Tissue

The creation of a testis organoid (artificial testis tissue) with sufficient resemblance to the complex form and function of the innate testis remains challenging, especially using non-rodent donor cells. Here, we report the generation of an organoid culture system with striking biomimicry of the native immature testis tissue, including vasculature. Using piglet testis cells as starting material, we optimized conditions for the formation of cell spheroids, followed by long-term culture in an air–liquid interface system. Both fresh and frozen-thawed cells were fully capable of self-reassembly into stable testis organoids consisting of tubular and interstitial compartments, with all major cell types and structural details expected in normal testis tissue. Surprisingly, our organoids also developed vascular structures; a phenomenon that has not been reported in any other culture system. In addition, germ cells do not decline over time, and Leydig cells release testosterone, hence providing a robust, tunable system for diverse basic and applied applications.

scholarly journals Exploring the structure and function of Thermotoga maritima CorA reveals the mechanism of gating and ion selectivity in Co2+/Mg2+ transport

2013 ◽  
Vol 451 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Nurhuda Nordin ◽  
Albert Guskov ◽  
Terri Phua ◽  
Newsha Sahaf ◽  
Yu Xia ◽  
...  
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Metal Ion ◽  
Thermotoga Maritima ◽  
Ion Selectivity ◽  
Metal Binding Sites ◽  
Gating Mechanism ◽  
Structural Details ◽  
And Function ◽  
Conserved Amino Acids

The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 Å (1 Å=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.

Comparison of elastic properties and contractile responses of isolated airway segments from mature and immature rabbits

2003 ◽  
Vol 95 (1) ◽  
pp. 265-271 ◽  
Author(s):  
R. Ramchandani ◽  
X. Shen ◽  
S. J. Gunst ◽  
R. S. Tepper
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Elastic Properties ◽  
Lung Parenchyma ◽  
Structure And Function ◽  
Airway Narrowing ◽  
Lower Shear ◽  
And Function ◽  
Immature Lung

Immature rabbits have greater maximal airway narrowing with bronchoconstriction in vivo compared with mature animals. As isolated immature lungs have a lower shear modulus, it is unclear whether the greater airway narrowing in the immature lung is secondary to less tethering between the airways and the lung parenchyma or to differences in the mechanical properties of the mature and immature airways. In the present study, we compared the mechanical properties of fluid-filled, isolated, intraparenchymal airway segments of the same generation from mature and immature rabbits. Stimulation with ACh resulted in greater airway narrowing in immature than mature bronchi. The immature bronchi were more compliant, had a lower resting airway volume, and were more collapsible compared with the mature bronchi. When the airways were contracted with ACh under isovolume conditions, the immature bronchi generated greater active pressure, and they were more sensitive to ACh than were mature bronchi. Our results suggest that maturational differences in the structure and function of the airways in the absence of the lung parenchyma can account for the greater maximal narrowing of immature than mature airways in vivo.

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