scholarly journals Ultrafast Brownian-ratchet mechanism for protein translocation by a AAA+ machine

2020 ◽  
Author(s):  
Hisham Mazal ◽  
Marija Iljina ◽  
Inbal Riven ◽  
Gilad Haran
Keyword(s):  
Single Molecule ◽  
Protein Translocation ◽  
Conformational Dynamics ◽  
Brownian Ratchet ◽  
Time Dynamics ◽  
Single Molecule Fret ◽  
Differential Behavior ◽  
Amplitude Fluctuations ◽  
Translocation Mechanism ◽  
Substrate Proteins

AbstractAAA+ ring-shaped machines, such as ClpB and Hsp104, mediate substrate translocation through their central channel by a set of pore loops. Recent structural studies suggested a universal hand-over-hand translocation mechanism, in which pore loops are moving rigidly in tandem with their corresponding subunits. However, functional and biophysical studies are in discord with this model. Here, we directly measure the real-time dynamics of the pore loops of ClpB and their response to substrate binding, using single-molecule FRET spectroscopy. All pore loops undergo large-amplitude fluctuations on the microsecond timescale, and change their conformation upon interaction with substrate proteins. Pore-loop conformational dynamics are modulated by nucleotides and strongly correlate with disaggregation activity. The differential behavior of the pore loops along the axial channel points to a fast Brownian-ratchet translocation mechanism, which likely acts in parallel to the much slower hand-over-hand process.

scholarly journals HDX-MS reveals nucleotide-regulated, anti-correlated opening and closure of SecA and SecY channels of the bacterial translocon

2019 ◽  
Author(s):  
Zainab Ahdash ◽  
Euan Pyle ◽  
William J. Allen ◽  
Robin A. Corey ◽  
Ian Collinson ◽  
...  
Keyword(s):  
Single Molecule ◽  
Conformational Changes ◽  
Protein Transport ◽  
Atp Hydrolysis ◽  
Protein Translocation ◽  
Conformational Dynamics ◽  
Brownian Ratchet ◽  
Exchange Mass Spectrometry ◽  
Dependent Transport ◽  
Hdx Ms

AbstractThe bacterial Sec translocon is a multi-component protein complex responsible for translocating diverse proteins across the plasma membrane. For post-translational protein translocation, the Sec-channel – SecYEG – associates with the motor protein SecA to mediate the ATP-dependent transport of unfolded pre-proteins across the membrane. Based on the structure of the machinery, combined with ensemble and single molecule analysis, a diffusional based Brownian ratchet mechanism for protein secretion has been proposed [Allen et al. eLife 2016;5:e15598]. However, the conformational dynamics required to facilitate this mechanism have not yet been fully resolved. Here, we employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to reveal striking nucleotide-dependent conformational changes in the Sec protein-channel. In addition to the ATP-dependent opening of SecY, reported previously, we observe a counteracting, also ATP-dependent, constriction of SecA around the mature regions of the pre-protein. Thus, ATP binding causes SecY to open and SecA to close, while ATP hydrolysis has the opposite effect. This alternating behaviour could help impose the directionality of the Brownian ratchet for protein transport through the Sec machinery, and possibly in translocation systems elsewhere. The results highlight the power of HDX-MS for interrogating the dynamic mechanisms of diverse membrane proteins; including their interactions with small molecules such as nucleotides (ATPases and GTPases) and inhibitors (e.g. antibiotics).

scholarly journals Two-way communication between SecY and SecA suggests a Brownian ratchet mechanism for protein translocation

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
William John Allen ◽  
Robin Adam Corey ◽  
Peter Oatley ◽  
Richard Barry Sessions ◽  
Steve A Baldwin ◽  
...  
Keyword(s):  
Single Molecule ◽  
Atp Hydrolysis ◽  
Protein Translocation ◽  
Md Simulations ◽  
Atp Binding ◽  
Nucleotide Exchange ◽  
Brownian Ratchet ◽  
Ratchet Mechanism ◽  
Single Molecule Fret ◽  
Directional Movement

The essential process of protein secretion is achieved by the ubiquitous Sec machinery. In prokaryotes, the drive for translocation comes from ATP hydrolysis by the cytosolic motor-protein SecA, in concert with the proton motive force (PMF). However, the mechanism through which ATP hydrolysis by SecA is coupled to directional movement through SecYEG is unclear. Here, we combine all-atom molecular dynamics (MD) simulations with single molecule FRET and biochemical assays. We show that ATP binding by SecA causes opening of the SecY-channel at long range, while substrates at the SecY-channel entrance feed back to regulate nucleotide exchange by SecA. This two-way communication suggests a new, unifying 'Brownian ratchet' mechanism, whereby ATP binding and hydrolysis bias the direction of polypeptide diffusion. The model represents a solution to the problem of transporting inherently variable substrates such as polypeptides, and may underlie mechanisms of other motors that translocate proteins and nucleic acids.

Conformational Dynamics of DNA Hairpins at Millisecond Resolution Obtained from Analysis of Single-Molecule FRET Histograms

2013 ◽  
Vol 117 (50) ◽  
pp. 16105-16109 ◽  
Author(s):  
Roman Tsukanov ◽  
Toma E. Tomov ◽  
Yaron Berger ◽  
Miran Liber ◽  
Eyal Nir
Keyword(s):  
Single Molecule ◽  
Conformational Dynamics ◽  
Dna Hairpins ◽  
Single Molecule Fret

scholarly journals Conformational dynamics of the ABC transporter McjD seen by single‐molecule FRET

2018 ◽  
Vol 37 (21) ◽  
Author(s):  
Florence Husada ◽  
Kiran Bountra ◽  
Konstantinos Tassis ◽  
Marijn Boer ◽  
Maria Romano ◽  
...  
Keyword(s):  
Abc Transporter ◽  
Single Molecule ◽  
Conformational Dynamics ◽  
Single Molecule Fret

scholarly journals Single Molecule FRET Studies of Protein Conformational Landscapes: 3 Prototypic Examples for the Relation Between Conformational Dynamics and Function

2011 ◽  
Vol 100 (3) ◽  
pp. 474a-475a
Author(s):  
Markus Richert ◽  
Dymitro Rodnin ◽  
Carola S. Hengstenberg ◽  
Thomas Peulen ◽  
Alessandro Valeri ◽  
...  
Keyword(s):  
Single Molecule ◽  
Conformational Dynamics ◽  
Single Molecule Fret ◽  
Dynamics And Function ◽  
And Function

scholarly journals Structural basis for the recognition of K48-linked Ub chain by proteasomal receptor Rpn13

2019 ◽  
Author(s):  
Zhu Liu ◽  
Xu Dong ◽  
Hua-Wei Yi ◽  
Ju Yang ◽  
Zhou Gong ◽  
...  
Keyword(s):  
Single Molecule ◽  
Complex Structure ◽  
Binding Mode ◽  
Structural Basis ◽  
Ubiquitinated Proteins ◽  
Single Molecule Fret ◽  
Compact State ◽  
A Charge ◽  
Substrate Proteins ◽  
Ubiquitinated Substrate

ABSTRACTThe interaction between K48-linked ubiquitin (Ub) chain and Rpn13 is important for proteasomal degradation of ubiquitinated substrate proteins. Only the complex structure between the N-terminal domain of Rpn13 (Rpn13NTD) and Ub monomer has been characterized, and it remains unclear how Rpn13 specifically recognizes K48-linked Ub chain. Using single-molecule FRET, here we show that K48-linked diubiquitin (K48-diUb) fluctuates among three distinct conformational states, and a preexisting compact state is selectively enriched by Rpn13NTD. The same binding mode is observed for full-length Rpn13 and longer K48-linked Ub chain. Using solution NMR spectroscopy, we have solved the complex structure between Rpn13NTD and K48-diUb. In the structure, Rpn13NTD simultaneously interacts with proximal and distal Ub subunits of K48-diUb that remain associated in the complex, thus corroborating smFRET findings. The proximal Ub interacts with Rpn13NTD similarly as the Ub monomer in the known Rpn13NTD:Ub structure, while the distal Ub binds to a largely electrostatic surface of Rpn13NTD. Thus, a charge reversal mutation in Rpn13NTD can weaken the interaction between Rpn13 and K48-linked Ub chain, causing accumulation of ubiquitinated proteins. Moreover, blockage of the access of the distal Ub to Rpn13NTD with a proximity attached Ub monomer can also disrupt the interaction between Rpn13 and K48-diUb. Together, the bivalent interaction of K48-linked Ub chain with Rpn13 provides the structural basis for Rpn13 linkage selectivity, which opens a new window for modulating proteasomal function.

scholarly journals 631: Single-molecule FRET reveals CFTR conformational dynamics during channel gating

2021 ◽  
Vol 20 ◽  
pp. S299-S300
Author(s):  
P. Liyanage ◽  
K. Mun ◽  
S. Yarlagadda ◽  
Y. Huang ◽  
A. Naren
Keyword(s):  
Single Molecule ◽  
Conformational Dynamics ◽  
Channel Gating ◽  
Single Molecule Fret

scholarly journals Conformational dynamics of Cas9 governing DNA cleavage revealed by single molecule FRET

2017 ◽  
Author(s):  
Mengyi Yang ◽  
Sijia Peng ◽  
Ruirui Sun ◽  
Jingdi Lin ◽  
Nan Wang ◽  
...  
Keyword(s):  
Single Molecule ◽  
Dna Cleavage ◽  
Conformational Dynamics ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Nuclease Activity ◽  
Single Molecule Fluorescence ◽  
Single Molecule Fret ◽  
Allosteric Communication ◽  
Target Binding

SummaryOff-target binding and cleavage by Cas9 pose as major challenges in its applications. How conformational dynamics of Cas9 governs its nuclease activity under on- and off-target conditions remains largely unknown. Here, using intra-molecular single molecule fluorescence resonance energy transfer measurements, we revealed that Cas9 in apo, sgRNA-bound, and dsDNA/sgRNA-bound forms all spontaneously transits between three major conformational states, mainly reflecting significant conformational mobility of the catalytic HNH domain. We furthermore uncovered a surprising long-range allosteric communication between the HNH domain and RNA/DNA heteroduplex at the PAM-distal end to ensure correct positioning of the catalytic site, which demonstrated a unique proofreading mechanism served as the last checkpoint before DNA cleavage. Several Cas9 residues were likely to mediate the allosteric communication and proofreading step. Modulating interactions between Cas9 and heteroduplex at the distal end by introducing mutations on these sites provides an alternative route to improve and optimize the CRISPR/Cas9 toolbox.

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