scholarly journals Cryo-EM of the ATP11C flippase reconstituted in Nanodiscs shows a distended phospholipid bilayer inner membrane around transmembrane helix 2

2021 ◽  
pp. 101498
Author(s):  
Hanayo Nakanishi ◽  
Kenichi Hayashida ◽  
Tomohiro Nishizawa ◽  
Atsunori Oshima ◽  
Kazuhiro Abe
Keyword(s):  
Transmembrane Helix ◽  
Phospholipid Bilayer ◽  
Inner Membrane

scholarly journals Differing Membrane Interactions of Two Highly Similar Drug-Metabolizing Cytochrome P450 Isoforms: CYP 2C9 and CYP 2C19

2019 ◽  
Vol 20 (18) ◽  
pp. 4328 ◽  
Author(s):  
Ghulam Mustafa ◽  
Prajwal P. Nandekar ◽  
Neil J. Bruce ◽  
Rebecca C. Wade
Keyword(s):  
Cytochrome P450 ◽  
Transmembrane Helix ◽  
Phospholipid Bilayer ◽  
Endoplasmic Reticulum Membrane ◽  
Globular Domain ◽  
Membrane Interactions ◽  
Membrane Bilayer ◽  
Similar Drug ◽  
Human Cytochrome ◽  
High Sequence Conservation

The human cytochrome P450 (CYP) 2C9 and 2C19 enzymes are two highly similar isoforms with key roles in drug metabolism. They are anchored to the endoplasmic reticulum membrane by their N-terminal transmembrane helix and interactions of their cytoplasmic globular domain with the membrane. However, their crystal structures were determined after N-terminal truncation and mutating residues in the globular domain that contact the membrane. Therefore, the CYP-membrane interactions are not structurally well-characterized and their dynamics and the influence of membrane interactions on CYP function are not well understood. We describe herein the modeling and simulation of CYP 2C9 and CYP 2C19 in a phospholipid bilayer. The simulations revealed that, despite high sequence conservation, the small sequence and structural differences between the two isoforms altered the interactions and orientations of the CYPs in the membrane bilayer. We identified residues (including K72, P73, and I99 in CYP 2C9 and E72, R73, and H99 in CYP 2C19) at the protein-membrane interface that contribute not only to the differing orientations adopted by the two isoforms in the membrane, but also to their differing substrate specificities by affecting the substrate access tunnels. Our findings provide a mechanistic interpretation of experimentally observed effects of mutagenesis on substrate selectivity.

scholarly journals Ferric Citrate Regulator FecR Is Translocated across the Bacterial Inner Membrane via a Unique Twin-Arginine Transport-Dependent Mechanism

2020 ◽  
Vol 202 (9) ◽  
Author(s):  
Ian J. Passmore ◽  
Jennifer M. Dow ◽  
Francesc Coll ◽  
Jon Cuccui ◽  
Tracy Palmer ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Sigma Factor ◽  
Signal Sequence ◽  
Transmembrane Helix ◽  
Ferric Citrate ◽  
Inner Membrane ◽  
Content Type ◽  
Signal Cascade ◽  
Tat System

ABSTRACT In Escherichia coli, citrate-mediated iron transport is a key nonheme pathway for the acquisition of iron. Binding of ferric citrate to the outer membrane protein FecA induces a signal cascade that ultimately activates the cytoplasmic sigma factor FecI, resulting in transcription of the fecABCDE ferric citrate transport genes. Central to this process is signal transduction mediated by the inner membrane protein FecR. FecR spans the inner membrane through a single transmembrane helix, which is flanked by cytoplasm- and periplasm-orientated moieties at the N and C termini. The transmembrane helix of FecR resembles a twin-arginine signal sequence, and the substitution of the paired arginine residues of the consensus motif decouples the FecR-FecI signal cascade, rendering the cells unable to activate transcription of the fec operon when grown on ferric citrate. Furthermore, the fusion of beta-lactamase C-terminal to the FecR transmembrane helix results in translocation of the C-terminal domain that is dependent on the twin-arginine translocation (Tat) system. Our findings demonstrate that FecR belongs to a select group of bitopic inner membrane proteins that contain an internal twin-arginine signal sequence. IMPORTANCE Iron is essential for nearly all living organisms due to its role in metabolic processes and as a cofactor for many enzymes. The FecRI signal transduction pathway regulates citrate-mediated iron import in many Gram-negative bacteria, including Escherichia coli. The interactions of FecR with the outer membrane protein FecA and cytoplasmic anti-sigma factor FecI have been extensively studied. However, the mechanism by which FecR inserts into the membrane has not previously been reported. In this study, we demonstrate that the targeting of FecR to the cytoplasmic membrane is dependent on the Tat system. As such, FecR represents a new class of bitopic Tat-dependent membrane proteins with an internal twin-arginine signal sequence.

scholarly journals Existence of Phospholipid Bilayer Structure in the Inner Membrane of Mitochondria

1972 ◽  
Vol 69 (11) ◽  
pp. 3412-3415 ◽  
Author(s):  
J. C. Hsia ◽  
W. L. Chen ◽  
R. A. Long ◽  
L. T. Wong ◽  
W. Kalow
Keyword(s):  
Phospholipid Bilayer ◽  
Bilayer Structure ◽  
Inner Membrane

scholarly journals The Inner Membrane Protein HrcV from Xanthomonas spp. Is Involved in Substrate Docking During Type III Secretion

2013 ◽  
Vol 26 (10) ◽  
pp. 1176-1189 ◽  
Author(s):  
Nadine Hartmann ◽  
Daniela Büttner
Keyword(s):  
Type Iii Secretion ◽  
Protein Function ◽  
Xanthomonas Campestris ◽  
Transmembrane Helix ◽  
Effector Proteins ◽  
Host Cells ◽  
System Component ◽  
Inner Membrane ◽  
Type Iii ◽  
Inner Membrane Protein

Pathogenicity of the gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a membrane-spanning type III secretion (T3S) system, which translocates effector proteins into eukaryotic host cells. In this study, we characterized the T3S system component HrcV, which is a member of the YscV/FlhA family of inner membrane proteins. HrcV consists of eight transmembrane helices and a cytoplasmic region (HrcVC). Mutant and protein–protein interaction studies showed that HrcVC is essential for protein function and binds to T3S substrates, including the early substrate HrpB2, the pilus protein HrpE, and effector proteins. Furthermore, HrcVC interacts with itself and with components and control proteins of the T3S apparatus. The interaction of HrcVC with HrpB2, HrpE, and T3S system components depends on amino acid residues in a conserved motif, designated flagella/hypersensitive response/invasion proteins export pore (FHIPEP), which is located in a cytoplasmic loop between transmembrane helix four and five of HrcV. Mutations in the FHIPEP motif abolish HrcV function but do not affect the interaction of HrcVC with effector proteins.

Factors Affecting the lnteraction of Tissue Factor/Factor Vll with Factor X in a Heterogeneous Tubular Reactor

1991 ◽  
Vol 65 (02) ◽  
pp. 139-143 ◽  
Author(s):  
Cynthia H Gemmell ◽  
Vincet T Turitto ◽  
Yale Nemerson
Keyword(s):  
Steady State ◽  
Tissue Factor ◽  
Factor Viia ◽  
Transmembrane Protein ◽  
Strong Association ◽  
Tubular Reactor ◽  
Factor Xa ◽  
Phospholipid Bilayer ◽  
Factor Vii ◽  
Factor X

SummaryA novel reactor recently described for studying phospholipiddependent blood coagulation reactions under flow conditions similar to those occurring in the vasculature has been further charactenzed. The reactor is a capitlary whose inner wall is coated with a stable phospholipid bilayer (or two bilayers) containing tissue factor, a transmembrane protein that is required for the enzymatic activation of factor X by factor VIIa. Perfusion of the capillary at wall shear rates ranging from 25 s−1 to 1,200 s−1 with purified bovine factors X and VIIa led to steady state factor Xa levels at the outlet. Assay were performed using a chromogenic substrate, SpectrozymeTMFXa, or by using a radiometric technique. In the absence of Ca2+ or factor VIIa there was no product formation. No difference was noted in the levels of factor Xa achieved when non-activated factor VII was perfused. Once steady state was achieved further factor Xa production continued in the absence of factor VIIa implying a very strong association of factor VIIa with the tissue factor in the phospholipid membrane. In agreement with static vesicle-type studies the reactor was sensitive to wall tissue factor concentration, temperature and the presence of phosphatidylserine in the bilayer.

Coaction of Electrostatic and Hydrophobic Interactions: Dynamic Constraints on Disordered TrkA Juxtamembrane Domain

2019 ◽  
Author(s):  
Zichen Wang ◽  
Huaxun Fan ◽  
Xiao Hu ◽  
John Khamo ◽  
Jiajie Diao ◽  
...  
Keyword(s):  
Single Molecule ◽  
Protein Function ◽  
Hydrophobic Interactions ◽  
Transmembrane Helix ◽  
Point Mutations ◽  
Salt Bridge ◽  
Receptor Activation ◽  
Membrane Dynamics ◽  
Juxtamembrane Domain ◽  
Joint Work

<p>The receptor tyrosine kinase family transmits signals into cell via a single transmembrane helix and a flexible juxtamembrane domain (JMD). Membrane dynamics makes it challenging to study the structural mechanism of receptor activation experimentally. In this study, we employ all-atom molecular dynamics with Highly Mobile Membrane-Mimetic to capture membrane interactions with the JMD of tropomyosin receptor kinase A (TrkA). We find that PIP<sub>2 </sub>lipids engage in lasting binding to multiple basic residues and compete with salt bridge within the peptide. We discover three residues insertion into the membrane, and perturb it through computationally designed point mutations. Single-molecule experiments indicate the contribution from hydrophobic insertion is comparable to electrostatic binding, and in-cell experiments show that enhanced TrkA-JMD insertion promotes receptor ubiquitination. Our joint work points to a scenario where basic and hydrophobic residues on disordered domains interact with lipid headgroups and tails, respectively, to restrain flexibility and potentially modulate protein function.</p>

Sign in / Sign up

Export Citation Format

Share Document