Asymmetric Stability among the Transmembrane Helices of Lactose Permease

Bennett, Michael; D'Rozario, Robert S. G.; Sansom, Mark S. P.; Yèagle, Philip L.

doi:10.1021/bi060355g

Cited by 23 publications

(20 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar observations were obtained in the simulation studies with ligand bound form of one of the well characterized MFS family members, LacY [58]. NMR studies have also shown that LacY domain D2 secondary structure is more stable than that of domain D1 [59]. In our glucose-ATP bound form simulation, domain D2 exhibited a significant conformational rearrangement and is seen as elevated RMSD.…”

Section: Resultssupporting

confidence: 86%

Molecular Dynamics Simulation Studies of GLUT4: Substrate-Free and Substrate-Induced Dynamics and ATP-Mediated Glucose Transport Inhibition

et al. 2010

View full text Add to dashboard Cite

BackgroundGlucose transporter 4 (GLUT4) is an insulin facilitated glucose transporter that plays an important role in maintaining blood glucose homeostasis. GLUT4 is sequestered into intracellular vesicles in unstimulated cells and translocated to the plasma membrane by various stimuli. Understanding the structural details of GLUT4 will provide insights into the mechanism of glucose transport and its regulation. To date, a crystal structure for GLUT4 is not available. However, earlier work from our laboratory proposed a well validated homology model for GLUT4 based on the experimental data available on GLUT1 and the crystal structure data obtained from the glycerol 3-phosphate transporter.Methodology/Principal FindingsIn the present study, the dynamic behavior of GLUT4 in a membrane environment was analyzed using three forms of GLUT4 (apo, substrate and ATP-substrate bound states). Apo form simulation analysis revealed an extracellular open conformation of GLUT4 in the membrane favoring easy exofacial binding of substrate. Simulation studies with the substrate bound form proposed a stable state of GLUT4 with glucose, which can be a substrate-occluded state of the transporter. Principal component analysis suggested a clockwise movement for the domains in the apo form, whereas ATP substrate-bound form induced an anti-clockwise rotation. Simulation studies suggested distinct conformational changes for the GLUT4 domains in the ATP substrate-bound form and favor a constricted behavior for the transport channel. Various inter-domain hydrogen bonds and switching of a salt-bridge network from E345-R350-E409 to E345-R169-E409 contributed to this ATP-mediated channel constriction favoring substrate occlusion and prevention of its release into cytoplasm. These data are consistent with the biochemical studies, suggesting an inhibitory role for ATP in GLUT-mediated glucose transport.Conclusions/SignificanceIn the absence of a crystal structure for any glucose transporter, this study provides mechanistic details of the conformational changes in GLUT4 induced by substrate and its regulator.

show abstract

Section: Resultssupporting

confidence: 86%

Molecular Dynamics Simulation Studies of GLUT4: Substrate-Free and Substrate-Induced Dynamics and ATP-Mediated Glucose Transport Inhibition

et al. 2010

View full text Add to dashboard Cite

show abstract

“…In at least one case , helix formation by an isolated TM segment could hence be shown to be independent of flanking hydrophilic residues (however, see Sections 3.2 and 5.2 for examples where this is not the case). More generally, organic solvents have proven useful in exploring the structural influence of tags (Tomich et al, 1998;Cano-Sanchez et al, 2006), comparing relative helical propensities of different peptides derived from the same membrane protein (Wigley et al, 1998;Lazarova et al, 2004;Bennett et al, 2006), and assessing the impact of disease-related mutations on TM peptide structure (Xie et al, 2000). In the latter case, the authors found that a TM peptide derived from a constitutively active mutant receptor displays a higher helical content than the wild-type peptide.…”

Section: Structure and Oligomerization Of Tm Peptides In Organic Solvmentioning

confidence: 99%

α-Helical transmembrane peptides: A “Divide and Conquer” approach to membrane proteins

Bordag¹,

Keller²

2010

Chemistry and Physics of Lipids

View full text Add to dashboard Cite

“…These focused on helix dynamics and stability,17 substrate binding,18; 19; 20; 21 and substrate transport pathway 1921; 22 Yin et al19 were the first to report any structural changes in LacY using a simulation approach.…”

Section: Introductionmentioning

confidence: 99%

Probing the Periplasmic-Open State of Lactose Permease in Response to Sugar Binding and Proton Translocation

Pendse¹,

Brooks²,

Klauda³

2010

Journal of Molecular Biology

View full text Add to dashboard Cite

Based on the crystal structure of lactose permease (LacY) open to the cytoplasm, a hybrid molecular simulation approach with self-guided Langevin dynamics (SGLD) is used to describe conformational changes that lead to a periplasmic-open state. This hybrid approach consists of implicit (IM) and explicit (EX) membrane simulations and requires SGLD to enhance protein motions during the IM simulations. The pore radius of the lumen increases by 3.5 Å on the periplasmic side and decreases by 2.5 Å on the cytoplasmic side (relative to the crystal structure), which suggest a lumen that is fully open to the periplasm to allow for extracellular sugar transport and closed to the cytoplasm. Based on our simulations, the mechanism that triggers this conformational change to the periplasmic-open state is the protonation Glu269 and binding of the disaccharide. Then, helix packing is destabilized by breaking of several side chains involved in hydrogen bonding (Asn245, Ser41, Glu374, Lys42 and Gln242). For the periplasmic-open conformations obtained from our simulations, helix-helix distances agree well with experimental measurements using double electron-electron resonance, fluorescence resonance energy transfer, and varying sized cross-linkers. The periplasmic-open conformations are also in compliance with various substrate accessibility/reactivity measurements that indicate an opening of the protein lumen on the periplasmic side on sugar binding. The comparison with these measurements suggests a possible incomplete closure of the cytoplasmic half in our simulations. However, the closure is sufficient to prevent the disaccharide from transporting to the cytoplasm, which is in accordance with the well-established alternating access model. Ser53, Gln60, and Phe354 are determined to be important in sugar transport during the periplasmic-open stage of the sugar transport cycle and the sugar is found to undergo an orientational change in order to escape the protein lumen.

show abstract

Asymmetric Stability among the Transmembrane Helices of Lactose Permease

Cited by 23 publications

References 44 publications

Molecular Dynamics Simulation Studies of GLUT4: Substrate-Free and Substrate-Induced Dynamics and ATP-Mediated Glucose Transport Inhibition

Molecular Dynamics Simulation Studies of GLUT4: Substrate-Free and Substrate-Induced Dynamics and ATP-Mediated Glucose Transport Inhibition

α-Helical transmembrane peptides: A “Divide and Conquer” approach to membrane proteins

Probing the Periplasmic-Open State of Lactose Permease in Response to Sugar Binding and Proton Translocation

Contact Info

Product

Resources

About