scholarly journals Molecular Dynamics of DNA Translocation by FtsK

2022 ◽  
Author(s):  
Joshua Pajak ◽  
Gaurav Arya
Keyword(s):  
Molecular Mechanisms ◽  
Atp Hydrolysis ◽  
Hydrolysis Product ◽  
Energy Landscapes ◽  
Dna Translocation ◽  
Product Release ◽  
Double Stranded Dna ◽  
A Subunit ◽  
Free Energy Landscapes ◽  
Compact Conformation

The bacterial FtsK motor harvests energy from ATP to translocate double-stranded DNA during cell division. Here, we probe the molecular mechanisms underlying coordinated DNA translocation in FtsK by performing long timescale simulations of its hexameric assembly and individual subunits. From these simulations we predict signaling pathways that connect the ATPase active site to DNA-gripping residues, which allows the motor to coordinate its translocation activity with its ATPase activity. Additionally, we utilize well-tempered metadynamics simulations to compute free-energy landscapes that elucidate the extended-to-compact transition involved in force generation. We show that nucleotide binding promotes a compact conformation of a motor subunit, whereas the apo subunit is flexible. Together, our results support a mechanism whereby each ATP-bound subunit of the motor conforms to the helical pitch of DNA, and ATP hydrolysis/product release causes a subunit to lose grip of DNA. By ordinally engaging and disengaging with DNA, the FtsK motor unidirectionally translocates DNA.

Regulation of ATP-dependent chromatin remodelers: accelerators/brakes, anchors and sensors

2018 ◽  
Vol 46 (6) ◽  
pp. 1423-1430 ◽  
Author(s):  
Somnath Paul ◽  
Blaine Bartholomew
Keyword(s):  
Protein Interactions ◽  
Atp Hydrolysis ◽  
Self Regulation ◽  
Protein Protein Interactions ◽  
Dna Translocation ◽  
Chromatin Remodelers ◽  
Histone Octamer ◽  
Double Stranded Dna ◽  
Accessory Subunits ◽  
Dna Translocase

All ATP-dependent chromatin remodelers have a DNA translocase domain that moves along double-stranded DNA when hydrolyzing ATP, which is the key action leading to DNA moving through nucleosomes. Recent structural and biochemical data from a variety of different chromatin remodelers have revealed that there are three basic ways in which these remodelers self-regulate their chromatin remodeling activity. In several instances, different domains within the catalytic subunit or accessory subunits through direct protein–protein interactions can modulate the ATPase and DNA translocation properties of the DNA translocase domain. These domains or subunits can stabilize conformations that either promote or interfere with the ability of the translocase domain to bind or retain DNA during translocation or alter the ability of the enzyme to hydrolyze ATP. Second, other domains or subunits are often necessary to anchor the remodeler to nucleosomes to couple DNA translocation and ATP hydrolysis to DNA movement around the histone octamer. These anchors provide a fixed point by which remodelers can generate sufficient torque to disrupt histone–DNA interactions and mobilize nucleosomes. The third type of self-regulation is in those chromatin remodelers that space nucleosomes or stop moving nucleosomes when a particular length of linker DNA has been reached. We refer to this third class as DNA sensors that can allosterically regulate nucleosome mobilization. In this review, we will show examples of these from primarily the INO80/SWR1, SWI/SNF and ISWI/CHD families of remodelers.

scholarly journals Sparse Epistatic Patterns in the Evolution of Terpene Synthases

2020 ◽  
Vol 37 (7) ◽  
pp. 1907-1924 ◽  
Author(s):  
Aditya Ballal ◽  
Caroline Laurendon ◽  
Melissa Salmon ◽  
Maria Vardakou ◽  
Jitender Cheema ◽  
...  
Keyword(s):  
Free Energy ◽  
Amino Acid ◽  
Molecular Mechanisms ◽  
Artemisia Annua ◽  
Hydrocarbon Chain ◽  
Reaction Rates ◽  
Energy Landscapes ◽  
Terpene Synthases ◽  
Specific Product ◽  
Free Energy Landscapes

Abstract We explore sequence determinants of enzyme activity and specificity in a major enzyme family of terpene synthases. Most enzymes in this family catalyze reactions that produce cyclic terpenes—complex hydrocarbons widely used by plants and insects in diverse biological processes such as defense, communication, and symbiosis. To analyze the molecular mechanisms of emergence of terpene cyclization, we have carried out in-depth examination of mutational space around (E)-β-farnesene synthase, an Artemisia annua enzyme which catalyzes production of a linear hydrocarbon chain. Each mutant enzyme in our synthetic libraries was characterized biochemically, and the resulting reaction rate data were used as input to the Michaelis–Menten model of enzyme kinetics, in which free energies were represented as sums of one-amino-acid contributions and two-amino-acid couplings. Our model predicts measured reaction rates with high accuracy and yields free energy landscapes characterized by relatively few coupling terms. As a result, the Michaelis–Menten free energy landscapes have simple, interpretable structure and exhibit little epistasis. We have also developed biophysical fitness models based on the assumption that highly fit enzymes have evolved to maximize the output of correct products, such as cyclic products or a specific product of interest, while minimizing the output of byproducts. This approach results in nonlinear fitness landscapes that are considerably more epistatic. Overall, our experimental and computational framework provides focused characterization of evolutionary emergence of novel enzymatic functions in the context of microevolutionary exploration of sequence space around naturally occurring enzymes.

scholarly journals Sparse epistatic patterns in the evolution of terpene synthases

2019 ◽  
Author(s):  
Aditya Ballal ◽  
Caroline Laurendon ◽  
Melissa Salmon ◽  
Maria Vardakou ◽  
Jitender Cheema ◽  
...  
Keyword(s):  
Free Energy ◽  
Amino Acid ◽  
Molecular Mechanisms ◽  
Fitness Landscape ◽  
Artemisia Annua ◽  
Reaction Rates ◽  
Energy Landscapes ◽  
Terpene Synthases ◽  
Specific Product ◽  
Free Energy Landscapes

AbstractWe explore sequence determinants of enzyme activity and specificity in a major enzyme family of terpene synthases. Most enzymes in this family catalyze reactions that produce cyclic terpenes – complex hydrocarbons widely used by plants and insects in diverse biological processes such as defense, communication, and symbiosis. To analyze the molecular mechanisms of emergence of terpene cyclization, we have carried out in-depth examination of mutational space around (E)-β-farnesene synthase, an Artemisia annua enzyme which catalyzes production of a linear hydrocarbon chain. Each mutant enzyme in our synthetic libraries was characterized biochemically, and the resulting reaction rate data was used as input to the Michaelis-Menten model of enzyme kinetics, in which free energies were represented as sums of one-amino-acid contributions and two-amino-acid couplings. Our model predicts measured reaction rates with high accuracy and yields free energy landscapes characterized by relatively few coupling terms. As a result, the Michaelis-Menten free energy landscapes have simple, interpretable structure and exhibit little epistasis. We have also developed biophysical fitness models based on the assumption that highly fit enzymes have evolved to maximize the output of correct products, such as cyclic products or a specific product of interest, while minimizing the output of byproducts. This approach results in a non-linear fitness landscape which is considerably more epistatic. Overall, our experimental and computational framework provides focused characterization of evolutionary emergence of novel enzymatic functions in the context of micro-evolutionary exploration of sequence space around naturally occurring enzymes.

scholarly journals Crystal structures of an E1–E2–ubiquitin thioester mimetic reveal molecular mechanisms of transthioesterification

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lingmin Yuan ◽  
Zongyang Lv ◽  
Melanie J. Adams ◽  
Shaun K. Olsen
Keyword(s):  
Complex Formation ◽  
Crystal Structures ◽  
Molecular Mechanisms ◽  
Conformational State ◽  
Biochemical Data ◽  
Conformational States ◽  
Product Release ◽  
Closed Conformation ◽  
Open Conformation ◽  
Conjugating Enzymes

AbstractE1 enzymes function as gatekeepers of ubiquitin (Ub) signaling by catalyzing activation and transfer of Ub to tens of cognate E2 conjugating enzymes in a process called E1–E2 transthioesterification. The molecular mechanisms of transthioesterification and the overall architecture of the E1–E2–Ub complex during catalysis are unknown. Here, we determine the structure of a covalently trapped E1–E2–ubiquitin thioester mimetic. Two distinct architectures of the complex are observed, one in which the Ub thioester (Ub(t)) contacts E1 in an open conformation and another in which Ub(t) instead contacts E2 in a drastically different, closed conformation. Altogether our structural and biochemical data suggest that these two conformational states represent snapshots of the E1–E2–Ub complex pre- and post-thioester transfer, and are consistent with a model in which catalysis is enhanced by a Ub(t)-mediated affinity switch that drives the reaction forward by promoting productive complex formation or product release depending on the conformational state.

scholarly journals Distributions of experimental protein structures on coarse-grained free energy landscapes

2015 ◽  
Vol 143 (24) ◽  
pp. 243153 ◽  
Author(s):  
Kannan Sankar ◽  
Jie Liu ◽  
Yuan Wang ◽  
Robert L. Jernigan
Keyword(s):  
Free Energy ◽  
Protein Structures ◽  
Coarse Grained ◽  
Energy Landscapes ◽  
Free Energy Landscapes
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