Generating force and movement is essential for the functions of cells and organisms. A variety of molecular motors that can move on tracks within cells have evolved to serve this role. How these ...motors interact with their tracks and how that, in turn, leads to the generation of force and movement is key to understanding the cellular roles that these motor-track systems serve. This review is focused on the best understood of these systems, which is the molecular motor myosin that moves on tracks of filamentous (F-) actin. The review highlights both the progress and the limits of our current understanding of how force generation can be controlled by F-actin–myosin interactions. What has emerged are insights they may serve as a framework for understanding the design principles of a number of types of molecular motors and their interactions with their tracks.
The derivatives of 1,2,4- triazole have attracted great attention among medicinal chemists due to their wide range of biological activity, good pharmacodynamic and pharmacokinetic profiles, and low ...toxicity, that necessitates the development of various synthesis methods and a comprehensive study of their reaction mechanisms. A detailed investigation of possible pathways for formation of new spiro-condensed 1,2,4triazolo1,5-cquinazolines, that combine two structural domains with different biological properties, was performed by computational study at the SMD/B3lyp/6-31+G(d) theory level. The mechanism of interaction between 2-(3-hetaryl-1,2,4-triazol-5-yl)phenylamine and cyclohexanone in methanol involves three main processes: formation of carbinolamine by addition of an amine to double bond C=O, elimination of a water molecule, and intramolecular cyclization leading to formation of spiro compounds. Results show increase in reactivity of reactants during acid-catalyzed reaction compared to uncatalyzed one. The nature of the heterocyclic substituent on the triazole ring has little effect on the reaction energy, while the mechanism is unchanged.
The actin and microtubule cytoskeletons play important roles in Golgi structure and function, but how they are connected remain poorly known. In this study, we investigated whether RAB6 GTPase, a ...Golgi-associated RAB involved in the regulation of several transport steps at the Golgi level, and two of its effectors, Myosin IIA and KIF20A participate in the coupling between actin and microtubule cytoskeleton. We have previously shown that RAB6-Myosin IIA interaction is critical for the fission of RAB6-positive transport carriers from Golgi/TGN membranes. Here we show that KIF20A is also involved in the fission process and serves to anchor RAB6 on Golgi/TGN membranes near microtubule nucleating sites. We provide evidence that the fission events occur at a limited number of hotspots sites. Our results suggest that coupling between actin and microtubule cytoskeletons driven by Myosin II and KIF20A ensures the spatial coordination between RAB6-positive vesicles fission from Golgi/TGN membranes and their exit along microtubules.
Force-producing ADP state of myosin bound to actin Wulf, Sarah F.; Ropars, Virginie; Fujita-Becker, Setsuko ...
Proceedings of the National Academy of Sciences - PNAS,
03/2016, Letnik:
113, Številka:
13
Journal Article
Recenzirano
Odprti dostop
Molecular motors produce force when they interact with their cellular tracks. For myosin motors, the primary force-generating state has MgADP tightly bound, whereas myosin is strongly bound to actin. ...We have generated an 8-Å cryoEM reconstruction of this state for myosin V and used molecular dynamics flexed fitting for model building. We compare this state to the subsequent state on actin (Rigor). The ADP-bound structure reveals that the actin-binding cleft is closed, even though MgADP is tightly bound. This state is accomplished by a previously unseen conformation of the β-sheet underlying the nucleotide pocket. The transition from the force-generating ADP state to Rigor requires a 9.5° rotation of the myosin lever arm, coupled to a β-sheet rearrangement. Thus, the structure reveals the detailed rearrangements underlying myosin force generation as well as the basis of strain-dependent ADP release that is essential for processive myosins, such as myosin V.
Membrane Type 1 Matrix Metalloprotease (MT1-MMP) contributes to the invasive progression of breast cancers by degrading extracellular matrix tissues. Nucleoside diphosphate kinase, NME1/NM23-H1, has ...been identified as a metastasis suppressor; however, its contribution to local invasion in breast cancer is not known. Here, we report that NME1 is up-regulated in ductal carcinoma in situ (DCIS) as compared to normal breast epithelial tissues. NME1 levels drop in microinvasive and invasive components of breast tumor cells relative to synchronous DCIS foci. We find a strong anti-correlation between NME1 and plasma membrane MT1-MMP levels in the invasive components of breast tumors, particularly in aggressive histological grade III and triple-negative breast cancers. Knockout of NME1 accelerates the invasive transition of breast tumors in the intraductal xenograft model. At the mechanistic level, we find that MT1-MMP, NME1 and dynamin-2, a GTPase known to require GTP production by NME1 for its membrane fission activity in the endocytic pathway, interact in clathrin-coated vesicles at the plasma membrane. Loss of NME1 function increases MT1-MMP surface levels by inhibiting endocytic clearance. As a consequence, the ECM degradation and invasive potentials of breast cancer cells are enhanced. This study identifies the down-modulation of NME1 as a potent driver of the in situ-to invasive transition during breast cancer progression.
There is growing evidence for a coupling of actin assembly and myosin motor activity in cells. However, mechanisms for recruitment of actin nucleators and motors on specific membrane compartments ...remain unclear. Here we report how Spir actin nucleators and myosin V motors coordinate their specific membrane recruitment. The myosin V globular tail domain (MyoV-GTD) interacts directly with an evolutionarily conserved Spir sequence motif. We determined crystal structures of MyoVa-GTD bound either to the Spir-2 motif or to Rab11 and show that a Spir-2:MyoVa:Rab11 complex can form. The ternary complex architecture explains how Rab11 vesicles support coordinated F-actin nucleation and myosin force generation for vesicle transport and tethering. New insights are also provided into how myosin activation can be coupled with the generation of actin tracks. Since MyoV binds several Rab GTPases, synchronized nucleator and motor targeting could provide a common mechanism to control force generation and motility in different cellular processes.
Myosin X has features not found in other myosins. Its structure must underlie its unique ability to generate filopodia, which are essential for neuritogenesis, wound healing, cancer metastasis and ...some pathogenic infections. By determining high-resolution structures of key components of this motor, and characterizing the in vitro behaviour of the native dimer, we identify the features that explain the myosin X dimer behaviour. Single-molecule studies demonstrate that a native myosin X dimer moves on actin bundles with higher velocities and takes larger steps than on single actin filaments. The largest steps on actin bundles are larger than previously reported for artificially dimerized myosin X constructs or any other myosin. Our model and kinetic data explain why these large steps and high velocities can only occur on bundled filaments. Thus, myosin X functions as an antiparallel dimer in cells with a unique geometry optimized for movement on actin bundles.
Mechanisms for formation and hydrolysis of biologically active 2-substituted 1,2,4triazolo1,5-
c
quinazolines were modeled at the SMD/B3LYP/6–31 + G(d) theory level. Obtained results revealed that ...internal heterocyclization of hetarylcarboxylic acid (3
H
-quinazolin-4-ylidene)-hydrazides involves a proton transfer from nitrogen atom of quinazoline system to oxygen atom of carbonyl group, cyclization with formation of 1,2,4triazolo4,3-
c
quinazoline system, elimination of molecule of water. Dimroth rearrangement using the ANRORC mechanism of 2-hetaryl1,2,4triazolo4,3-
c
quinazolines leads to 2-hetaryl1,2,4triazolo1,5-
c
quinazolines. The rearrangement is catalyzed by molecule of water and consists of an addition of molecule of water to quinazoline cycle that facilitates its sequential opening, rotation of 1,2,4-triazole, cycle closure and elimination of molecule of water. Acid-catalyzed hydrolysis of 2-hetaryl1,2,4triazolo1,5-
c
quinazolines involves protonation of nitrogen atom of quinazoline cycle, an addition of molecule of water to protonated 1,2,4triazolo1,5-
c
quinazoline system, opening of quinazoline cycle, an addition of second molecule of water, elimination of formic acid, and deprotonation. Substituents influence insignificantly on activation barriers for formation and hydrolysis of 2-hetaryl1,2,4triazolo1,5-
c
quinazolines.
1,2,4-Triazole is a popular scaffold in drug design. According to chemical nature, the triazole ring tends to prototropic tautomerism. Tautomeric phenomena are important for studying the chemical ...reactivity and interaction of drugs based on triazole with biomolecules in the human body. Theoretical modeling was used to assign structures of newly synthesized 2-(3-hetaryl-1,2,4-triazol-5-yl)anilines. The procedure included quantum-chemical SMD/M06-2X/6–311++G(d,p) calculation of the relative stability for possible tautomers, simulation of UV/vis spectra for the most stable forms, and comparison of the resulting curves with the experimental spectral data taking into account the Boltzmann weighting. The influence of the substituents in triazole ring on tautomeric equilibrium was elucidated. NBO charge distribution, dipole moment, molecular electrostatic potential, and HOMO/LUMO gap for the most stable tautomers were analyzed.
Specific recognition of the cargo that molecular motors transport or tether to cytoskeleton tracks allows them to perform precise cellular functions at particular times and positions in cells. ...However, very little is known about how evolution has favored conservation of functions for some isoforms, while also allowing for the generation of new recognition sites and specialized cellular functions. Here we present several crystal structures of the myosin Va or the myosin Vb globular tail domain (GTD) that gives insights into how the motor is linked to the recycling membrane compartments via Rab11 or to the melanosome membrane via recognition of the melanophilin adaptor that binds to Rab27a. The structures illustrate how the Rab11-binding site has been conserved during evolution and how divergence at another site of the GTD allows more specific interactions such as the specific recognition of melanophilin by the myosin Va isoform. With atomic structural insights, these structures also show how either the partner or the GTD structural plasticity upon association is critical for selective recruitment of the motor.
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