Chemo-Mechanical Coupling in the Transport Cycle of a Heme ABC Transporter

2019 ◽  
Vol 123 (34) ◽  
pp. 7270-7281 ◽  
Author(s):  
Koichi Tamura ◽  
Hiroshi Sugimoto ◽  
Yoshitsugu Shiro ◽  
Yuji Sugita
Keyword(s):  
Abc Transporter ◽  
Mechanical Coupling ◽  
Transport Cycle

scholarly journals Characterizing Transition Pathways in the Transport Cycle of ABC Transporter MsbA

2012 ◽  
Vol 102 (3) ◽  
pp. 446a
Author(s):  
Wenxun Gan ◽  
Mahmoud Moradi ◽  
Emad Tajkhorshid
Keyword(s):  
Abc Transporter ◽  
Transition Pathways ◽  
Transport Cycle

scholarly journals Conformational changes in the yeast mitochondrial ABC transporter Atm1 during the transport cycle

2021 ◽  
Vol 7 (52) ◽  
Author(s):  
Thomas L. Ellinghaus ◽  
Thomas Marcellino ◽  
Vasundara Srinivasan ◽  
Roland Lill ◽  
Werner Kühlbrandt
Keyword(s):  
Abc Transporter ◽  
Conformational Changes ◽  
Transport Cycle

scholarly journals Combining Mutations That Inhibit Two Distinct Steps of the ATP Hydrolysis Cycle Restores Wild-Type Function in the Lipopolysaccharide Transporter and Shows that ATP Binding Triggers Transport

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Brent W. Simpson ◽  
Karanbir S. Pahil ◽  
Tristan W. Owens ◽  
Emily A. Lundstedt ◽  
Rebecca M. Davis ◽  
...  
Keyword(s):  
Abc Transporter ◽  
Conformational Changes ◽  
Abc Transporters ◽  
Atp Binding ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Lethal Effects ◽  
Gram Negative ◽  
Binding Domains ◽  
Transport Cycle

ABSTRACT ATP-binding cassette (ABC) transporters constitute a large family of proteins present in all domains of life. They are powered by dynamic ATPases that harness energy from binding and hydrolyzing ATP through a cycle that involves the closing and reopening of their two ATP-binding domains. The LptB2FGC exporter is an essential ABC transporter that assembles lipopolysaccharides (LPS) on the surface of Gram-negative bacteria to form a permeability barrier against many antibiotics. LptB2FGC extracts newly synthesized LPS molecules from the inner membrane and powers their transport across the periplasm and through the outer membrane. How LptB2FGC functions remains poorly understood. Here, we show that the C-terminal domain of the dimeric LptB ATPase is essential for LPS transport in Escherichia coli. Specific changes in the C-terminal domain of LptB cause LPS transport defects that can be repaired by intragenic suppressors altering the ATP-binding domains. Surprisingly, we found that each of two lethal changes in the ATP-binding and C-terminal domains of LptB, when present in combined form, suppressed the defects associated with the other to restore LPS transport to wild-type levels both in vivo and in vitro. We present biochemical evidence explaining the effect that each of these mutations has on LptB function and how the observed cosuppression results from the opposing lethal effects these changes have on the dimerization state of the LptB ATPase. We therefore propose that these sites modulate the closing and reopening of the LptB dimer, providing insight into how the LptB2FGC transporter cycles to export LPS to the cell surface and how to inhibit this essential envelope biogenesis process. IMPORTANCE Gram-negative bacteria are naturally resistant to many antibiotics because their surface is covered by the glycolipid LPS. Newly synthesized LPS is transported across the cell envelope by the multiprotein Lpt machinery, which includes LptB2FGC, an unusual ABC transporter that extracts LPS from the inner membrane. Like in other ABC transporters, the LptB2FGC transport cycle is driven by the cyclical conformational changes that a cytoplasmic, dimeric ATPase, LptB, undergoes when binding and hydrolyzing ATP. How these conformational changes are controlled in ABC transporters is poorly understood. Here, we identified two lethal changes in LptB that, when combined, remarkably restore wild-type transport function. Biochemical studies revealed that the two changes affect different steps in the transport cycle, having opposing, lethal effects on LptB’s dimerization cycle. Our work provides mechanistic details about the LptB2FGC extractor that could be used to develop Lpt inhibitors that would overcome the innate antibiotic resistance of Gram-negative bacteria.

scholarly journals Chemo-mechanical Coupling in the Transport Cycle of a Type II ABC Transporter

2018 ◽  
Author(s):  
Koichi Tamura ◽  
Hiroshi Sugimoto ◽  
Yoshitsugu Shiro ◽  
Yuji Sugita
Keyword(s):  
Atpase Activity ◽  
Abc Transporter ◽  
Conformational Changes ◽  
Abc Transporters ◽  
Md Simulations ◽  
Coupling Mechanism ◽  
Transmembrane Helices ◽  
Mechanical Coupling ◽  
Binding Domains ◽  
Wide Range

AbstractAT P -binding cassette (ABC) transporters are integral membrane proteins that translocate a wide range of substrates across biological membranes, harnessing free energy from the binding and hydrolysis of ATP. To understand the mechanism of the inward- to outward-facing transition that could be achieved by tight regulation of ATPase activity through extensive conformational changes of the protein, we applied template-based iterative all-atom molecular dynamics (MD) simulation to the heme ABC transporter BhuUV-T. The simulations, together with biased MDs, predict two new conformations of the protein, namely, occluded (Occ) and outward-facing (OF) conformations. The comparison between the inward-facing crystal structure and the predicted two structures shows atomic details of the gating motions at the transmembrane helices and dimerization of the nucleotide-binding domains (NBDs). The MD simulations further reveal a novel role of the ABC signature motifs (LSGG[Q/E]) at the NBDs in decelerating ATPase activity in the Occ form through sporadic flipping of the side chains of the LSGG[Q/E] catalytic serine residues. The orientational changes are coupled to loose NBD dimerization in the Occ state, whereas they are blocked in the OF form where the NBDs are tightly dimerized. The chemo-mechanical coupling mechanism may apply to other types of ABC transporters having the conserved LSGG[Q/E] signature motifs.

LXR und ABC-Transporter-Expression im Trophoblasten bei IUGR

2017 ◽  
Vol 77 (04) ◽  
pp. 379-395
Author(s):  
L Schmieding ◽  
A Klein ◽  
N Maass ◽  
C Eckmann-Scholz ◽  
D Lütjohann ◽  
...  
Keyword(s):  
Abc Transporter ◽  
Transporter Expression

ABC-Transporter Gen-Polymorphismen als potentielle Prädiktoren der therapeutischen Effizienz von Mitoxantron bei Multipler Sklerose

2007 ◽  
Vol 34 (S 2) ◽  
Author(s):  
S Cotte ◽  
N Kruse ◽  
N Ahsen ◽  
UK Zettl ◽  
R Gold ◽  
...  
Keyword(s):  
Abc Transporter

A two degrees of freedom comb capacitive-type accelerometer with low cross-axis sensitivity

2019 ◽  
Vol 13 (3) ◽  
pp. 5334-5346
Author(s):  
M. N. Nguyen ◽  
L. Q. Nguyen ◽  
H. M. Chu ◽  
H. N. Vu
Keyword(s):  
Degrees Of Freedom ◽  
Proof Mass ◽  
Vibration Modes ◽  
Electrode Structure ◽  
Element Analysis ◽  
Mechanical Coupling ◽  
Fully Differential ◽  
Mode Effects ◽  
The Finite Element Analysis ◽  
Cross Axis

In this paper, we report on a SOI-based comb capacitive-type accelerometer that senses acceleration in two lateral directions. The structure of the accelerometer was designed using a proof mass connected by four folded-beam springs, which are compliant to inertial displacement causing by attached acceleration in the two lateral directions. At the same time, the folded-beam springs enabled to suppress cross-talk causing by mechanical coupling from parasitic vibration modes. The differential capacitor sense structure was employed to eliminate common mode effects. The design of gap between comb fingers was also analyzed to find an optimally sensing comb electrode structure. The design of the accelerometer was carried out using the finite element analysis. The fabrication of the device was based on SOI-micromachining. The characteristics of the accelerometer have been investigated by a fully differential capacitive bridge interface using a sub-fF switched-capacitor integrator circuit. The sensitivities of the accelerometer in the two lateral directions were determined to be 6 and 5.5 fF/g, respectively. The cross-axis sensitivities of the accelerometer were less than 5%, which shows that the accelerometer can be used for measuring precisely acceleration in the two lateral directions. The accelerometer operates linearly in the range of investigated acceleration from 0 to 4g. The proposed accelerometer is expected for low-g applications.

Molecular Basis of Glucose Transport Mechanism in Plants

2019 ◽  
Author(s):  
Balaji Selvam ◽  
Ya-Chi Yu ◽  
Liqing Chen ◽  
Diwakar Shukla
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Molecular Dynamics Simulations ◽  
Conformational Changes ◽  
Transport Mechanism ◽  
Conformational Dynamics ◽  
Site Directed Mutagenesis ◽  
Free Energy Barrier ◽  
Transport Cycle ◽  
Dynamics Simulations

<p>The SWEET family belongs to a class of transporters in plants that undergoes large conformational changes to facilitate transport of sugar molecules across the cell membrane. However, the structures of their functionally relevant conformational states in the transport cycle have not been reported. In this study, we have characterized the conformational dynamics and complete transport cycle of glucose in OsSWEET2b transporter using extensive molecular dynamics simulations. Using Markov state models, we estimated the free energy barrier associated with different states as well as 1 for the glucose the transport mechanism. SWEETs undergoes structural transition to outward-facing (OF), Occluded (OC) and inward-facing (IF) and strongly support alternate access transport mechanism. The glucose diffuses freely from outside to inside the cell without causing major conformational changes which means that the conformations of glucose unbound and bound snapshots are exactly same for OF, OC and IF states. We identified a network of hydrophobic core residues at the center of the transporter that restricts the glucose entry to the cytoplasmic side and act as an intracellular hydrophobic gate. The mechanistic predictions from molecular dynamics simulations are validated using site-directed mutagenesis experiments. Our simulation also revealed hourglass like intermediate states making the pore radius narrower at the center. This work provides new fundamental insights into how substrate-transporter interactions actively change the free energy landscape of the transport cycle to facilitate enhanced transport activity.</p>

Sign in / Sign up

Export Citation Format

Share Document