scholarly journals The working stroke of the myosin II motor in muscle is not tightly coupled to release of orthophosphate from its active site

2013 ◽  
Vol 591 (20) ◽  
pp. 5187-5205 ◽  
Author(s):  
Marco Caremani ◽  
Luca Melli ◽  
Mario Dolfi ◽  
Vincenzo Lombardi ◽  
Marco Linari
Keyword(s):  
Active Site ◽  
Myosin Ii ◽  
Tightly Coupled

scholarly journals Amino acid sequence of the active site of Acanthamoeba myosin II.

1986 ◽  
Vol 261 (4) ◽  
pp. 1844-1848
Author(s):  
M A Atkinson ◽  
E A Robinson ◽  
E Appella ◽  
E D Korn
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Active Site ◽  
Myosin Ii

scholarly journals Assembly of a dsRNA synthesizing complex: RNA-DEPENDENT RNA POLYMERASE 2 contacts the largest subunit of NUCLEAR RNA POLYMERASE IV

2021 ◽  
Vol 118 (13) ◽  
pp. e2019276118
Author(s):  
Vibhor Mishra ◽  
Jasleen Singh ◽  
Feng Wang ◽  
Yixiang Zhang ◽  
Akihito Fukudome ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Active Site ◽  
Rna Dependent Rna Polymerase ◽  
Dna Viruses ◽  
Selfish Genetic Elements ◽  
Pol Iv ◽  
Nuclear Rna ◽  
Tightly Coupled ◽  
Rna Polymerase Iv ◽  
Nuclear Rna Polymerase

In plants, transcription of selfish genetic elements such as transposons and DNA viruses is suppressed by RNA-directed DNA methylation. This process is guided by 24-nt short-interfering RNAs (siRNAs) whose double-stranded precursors are synthesized by DNA-dependent NUCLEAR RNA POLYMERASE IV (Pol IV) and RNA-DEPENDENT RNA POLYMERASE 2 (RDR2). Pol IV and RDR2 coimmunoprecipitate, and their activities are tightly coupled, yet the basis for their association is unknown. Here, we show that an interval near the RDR2 active site contacts the Pol IV catalytic subunit, NRPD1, the largest of Pol IV’s 12 subunits. Contacts between the catalytic regions of the two enzymes suggests that RDR2 is positioned to rapidly engage the free 3′ ends of Pol IV transcripts and convert these single-stranded transcripts into double-stranded RNAs (dsRNAs).

scholarly journals Magnesium-Dependence and Active Site Dynamics in Myosin V and Myosin II

2013 ◽  
Vol 104 (2) ◽  
pp. 642a-643a
Author(s):  
Anja M. Swenson ◽  
Joseph M. Muretta ◽  
Faith D' Amico ◽  
William C. Unrath ◽  
David D. Thomas ◽  
...  
Keyword(s):  
Active Site ◽  
Myosin Ii ◽  
Myosin V

scholarly journals Actomyosin sliding is attenuated in contractile biomimetic cortices

2014 ◽  
Vol 25 (12) ◽  
pp. 1845-1853 ◽  
Author(s):  
Michael Murrell ◽  
Margaret L. Gardel
Keyword(s):  
Cell Shape ◽  
Myosin Ii ◽  
Actin Cortex ◽  
Nonmuscle Cells ◽  
Tightly Coupled ◽  
Contractile Forces ◽  
High Degree

Myosin II motors embedded within the actin cortex generate contractile forces to modulate cell shape in essential behaviors, including polarization, migration, and division. In sarcomeres, myosin II–mediated sliding of antiparallel F-actin is tightly coupled to myofibril contraction. By contrast, cortical F-actin is highly disordered in polarity, orientation, and length. How the disordered nature of the actin cortex affects actin and myosin movements and resultant contraction is unknown. Here we reconstitute a model cortex in vitro to monitor the relative movements of actin and myosin under conditions that promote or abrogate network contraction. In weakly contractile networks, myosin can translocate large distances across stationary F-actin. By contrast, the extent of relative actomyosin sliding is attenuated during contraction. Thus actomyosin sliding efficiently drives contraction in actomyosin networks despite the high degree of disorder. These results are consistent with the nominal degree of relative actomyosin movement observed in actomyosin assemblies in nonmuscle cells.

scholarly journals Pulsatile actomyosin contractions underlie Par polarity during the neuroblast polarity cycle

2021 ◽  
Author(s):  
Chet Huan Oon ◽  
Kenneth E. Prehoda
Keyword(s):  
Protein Dynamics ◽  
Myosin Ii ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Par Proteins ◽  
Apical Pole ◽  
Tightly Coupled ◽  
Early Mitosis

AbstractThe Par complex is polarized to the apical cortex of asymmetrically dividing Drosophila neuroblasts. Previously we showed that Par proteins are polarized by apically directed cortical movements that require F-actin (Oon and Prehoda, 2019). Here we report the discovery of cortical actin pulses that begin before the Par complex is recruited to the cell cortex and ultimately become tightly coupled to Par protein dynamics. Pulses are initially unoriented in interphase but are rapidly directed towards the apical pole in early mitosis, shortly before the Par protein aPKC accumulates on the cortex. The movements of cortical aPKC that lead to its polarization are precisely correlated with cortical actin pulses and F-actin disruption coincides with immediate loss of movement followed by depolarization. We find that myosin II is a component of the cortical pulses, suggesting that actomyosin pulsatile contractions initiate and maintain apical Par polarity during the neuroblast polarity cycle.

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Structures of c-di-GMP/cGAMP degrading phosphodiesterase VcEAL: identification of a novel conformational switch and its implication

2019 ◽  
Vol 476 (21) ◽  
pp. 3333-3353 ◽  
Author(s):  
Malti Yadav ◽  
Kamalendu Pal ◽  
Udayaditya Sen
Keyword(s):  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Triosephosphate Isomerase ◽  
Catalytic Mechanism ◽  
Degradation Mechanism ◽  
Structural Basis ◽  
Conserved Residues ◽  
Phosphodiester Bond ◽  
Cyclic Dinucleotides

Cyclic dinucleotides (CDNs) have emerged as the central molecules that aid bacteria to adapt and thrive in changing environmental conditions. Therefore, tight regulation of intracellular CDN concentration by counteracting the action of dinucleotide cyclases and phosphodiesterases (PDEs) is critical. Here, we demonstrate that a putative stand-alone EAL domain PDE from Vibrio cholerae (VcEAL) is capable to degrade both the second messenger c-di-GMP and hybrid 3′3′-cyclic GMP–AMP (cGAMP). To unveil their degradation mechanism, we have determined high-resolution crystal structures of VcEAL with Ca2+, c-di-GMP-Ca2+, 5′-pGpG-Ca2+ and cGAMP-Ca2+, the latter provides the first structural basis of cGAMP hydrolysis. Structural studies reveal a typical triosephosphate isomerase barrel-fold with substrate c-di-GMP/cGAMP bound in an extended conformation. Highly conserved residues specifically bind the guanine base of c-di-GMP/cGAMP in the G2 site while the semi-conserved nature of residues at the G1 site could act as a specificity determinant. Two metal ions, co-ordinated with six stubbornly conserved residues and two non-bridging scissile phosphate oxygens of c-di-GMP/cGAMP, activate a water molecule for an in-line attack on the phosphodiester bond, supporting two-metal ion-based catalytic mechanism. PDE activity and biofilm assays of several prudently designed mutants collectively demonstrate that VcEAL active site is charge and size optimized. Intriguingly, in VcEAL-5′-pGpG-Ca2+ structure, β5–α5 loop adopts a novel conformation that along with conserved E131 creates a new metal-binding site. This novel conformation along with several subtle changes in the active site designate VcEAL-5′-pGpG-Ca2+ structure quite different from other 5′-pGpG bound structures reported earlier.

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