scholarly journals The crystal structure of bromide-bound GtACR1 reveals a pre-activated state in the transmembrane anion tunnel

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Hai Li ◽  
Chia-Ying Huang ◽  
Elena G Govorunova ◽  
Oleg A Sineshchekov ◽  
Adrian Yi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structural Changes ◽  
Anion Channel ◽  
Salt Bridge ◽  
Activation Mechanism ◽  
Research Article ◽  
Channel Opening ◽  
Activated State ◽  
Gated Channel ◽  
Switch Mechanism

The crystal structure of the light-gated anion channel GtACR1 reported in our previous Research Article (Li et al., 2019) revealed a continuous tunnel traversing the protein from extracellular to intracellular pores. We proposed the tunnel as the conductance channel closed by three constrictions: C1 in the extracellular half, mid-membrane C2 containing the photoactive site, and C3 on the cytoplasmic side. Reported here, the crystal structure of bromide-bound GtACR1 reveals structural changes that relax the C1 and C3 constrictions, including a novel salt-bridge switch mechanism involving C1 and the photoactive site. These findings indicate that substrate binding induces a transition from an inactivated state to a pre-activated state in the dark that facilitates channel opening by reducing free energy in the tunnel constrictions. The results provide direct evidence that the tunnel is the closed form of the channel of GtACR1 and shed light on the light-gated channel activation mechanism.

scholarly journals The Crystal Structure of Bromide-Bound GtACR1 Reveals a Pre-Activated State in the Transmembrane Anion Tunnel

2021 ◽  
Author(s):  
Hai Li ◽  
Chia-Ying Huang ◽  
Elena G. Govorunova ◽  
Oleg A. Sineshchekov ◽  
Meitian Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structural Changes ◽  
Anion Channel ◽  
Salt Bridge ◽  
Chemical Mechanism ◽  
Activation Mechanism ◽  
Anion Conductance ◽  
Channel Opening ◽  
Activated State ◽  
Gated Channel

AbstractThe crystal structure of the light-gated anion channel GtACR1 reported in our previous research article (Li et al., 2019) revealed a continuous tunnel traversing the protein from extracellular to intracellular pores. We proposed the tunnel as the conductance channel closed by three constrictions: C1 in the extracellular half, mid-membrane C2 containing the photoactive site, and C3 on the cytoplasmic side. Reported here, the crystal structure of bromide-bound GtACR1 reveals structural changes that relax the C1 and C3 constrictions, including a novel salt-bridge switch mechanism involving C1 and the photoactive site. These findings indicate that substrate binding induces a transition from an inactivated state to a pre-activated state in the dark that facilitates channel opening by reducing free energy in the tunnel constrictions. The results provide direct evidence that the tunnel is the closed form of the channel of GtACR1 and shed light on the light-gated channel activation mechanism.Impact StatementSubstrate-induced structural changes in GtACR1 provide new insight into the chemical mechanism of natural light-gated anion conductance, and facilitate its optimization for photoinhibition of neuron firing in optogenetics.

scholarly journals Crystal Structure of MtaN, a Global Multidrug Transporter Gene Activator

2001 ◽  
Vol 276 (50) ◽  
pp. 47178-47184 ◽  
Author(s):  
Michael H. Godsey ◽  
Natalya N. Baranova ◽  
Alexander A. Neyfakh ◽  
Richard G. Brennan
Keyword(s):  
Crystal Structure ◽  
Family Member ◽  
Structural Changes ◽  
Coiled Coil ◽  
Activation Mechanism ◽  
Multidrug Transporter ◽  
Hydrophobic Core ◽  
Winged Helix ◽  
Truncation Mutant ◽  
Antiparallel Coiled Coil

MtaN (Multidrug Transporter Activation, N terminus) is a constitutive, transcriptionally active 109-residue truncation mutant, which contains only the N-terminal DNA-binding and dimerization domains of MerR family member Mta. The 2.75 Å resolution crystal structure of apo-MtaN reveals a winged helix-turn-helix protein with a protruding 8-turn helix (α5) that is involved in dimerization by the formation of an antiparallel coiled-coil. The hydrophobic core and helices α1 through α4 are structurally homologous to MerR family member BmrR bound to DNA, whereas one wing (Wing 1) is shifted. Differences between the orientation of α5 with respect to the core and the revolution of the antiparallel coiled-coil lead to significantly altered conformations of MtaN and BmrR dimers. These shifts result in a conformation of MtaN that appears to be incompatible with the transcription activation mechanism of BmrR and suggest that additional DNA-induced structural changes are necessary.

scholarly journals Structural Changes in the Acceptor Site of Photosystem II upon Ca2+/Sr2+ Exchange in the Mn4CaO5 Cluster Site and the Possible Long-Range Interactions

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 371
Author(s):  
Koua
Keyword(s):  
Crystal Structure ◽  
Photosystem Ii ◽  
Long Range ◽  
Electron Acceptor ◽  
Structural Changes ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Long Range Interactions ◽  
Structural Perturbations ◽  
Oxygen Evolving

The Mn4CaO5 cluster site in the oxygen-evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long-range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr-PSII resolved at 2.1 Å and compared it with the native Ca-PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long-range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.

scholarly journals Deacetylation as a receptor-regulated direct activation switch for pannexin channels

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu-Hsin Chiu ◽  
Christopher B. Medina ◽  
Catherine A. Doyle ◽  
Ming Zhou ◽  
Adishesh K. Narahari ◽  
...  
Keyword(s):  
G Protein Coupled Receptors ◽  
Activation Mechanism ◽  
Lysine Acetylation ◽  
Intercellular Signaling ◽  
Histone Deacetylase 6 ◽  
Pannexin 1 ◽  
Lysine Deacetylase ◽  
Channel Opening ◽  
Lysine Residues ◽  
G Protein Coupled

AbstractActivation of Pannexin 1 (PANX1) ion channels causes release of intercellular signaling molecules in a variety of (patho)physiological contexts. PANX1 can be activated by G protein-coupled receptors (GPCRs), including α1-adrenergic receptors (α1-ARs), but how receptor engagement leads to channel opening remains unclear. Here, we show that GPCR-mediated PANX1 activation can occur via channel deacetylation. We find that α1-AR-mediated activation of PANX1 channels requires Gαq but is independent of phospholipase C or intracellular calcium. Instead, α1-AR-mediated PANX1 activation involves RhoA, mammalian diaphanous (mDia)-related formin, and a cytosolic lysine deacetylase activated by mDia – histone deacetylase 6. HDAC6 associates with PANX1 and activates PANX1 channels, even in excised membrane patches, suggesting direct deacetylation of PANX1. Substitution of basally-acetylated intracellular lysine residues identified on PANX1 by mass spectrometry either prevents HDAC6-mediated activation (K140/409Q) or renders the channels constitutively active (K140R). These data define a non-canonical RhoA-mDia-HDAC6 signaling pathway for GαqPCR activation of PANX1 channels and uncover lysine acetylation-deacetylation as an ion channel silencing-activation mechanism.

scholarly journals All-Atom MD Simulations of the HBV Capsid Complexed with AT130 Reveal Secondary and Tertiary Structural Changes and Mechanisms of Allostery

2021 ◽  
Author(s):  
Carolina Pérez Segura ◽  
Boon Chong Goh ◽  
Jodi A. Hadden-Perilla
Keyword(s):  
Small Molecules ◽  
Drug Target ◽  
Structural Changes ◽  
Salt Bridge ◽  
Md Simulations ◽  
Health Concern ◽  
Protein Dimer ◽  
B Virus ◽  
Flexible Protein ◽  
Dynamics Simulations

AbstractThe hepatitis B virus (HBV) capsid is an attractive drug target, relevant to combating viral hepatitis as a major public health concern. Among small molecules known to interfere with capsid assembly, the phenylpropenamides, including AT130, represent an important anti-viral paradigm based on disrupting the timing of genome encapsulation. Crystallographic studies of AT130-bound complexes have been essential in explaining the effects of the small molecule on HBV capsid structure; however, computational examination reveals that key changes attributed to AT130 were erroneous, likely a consequence of interpreting poor resolution arising from a highly flexible protein. Here, all-atom molecular dynamics simulations of an intact AT130-bound HBV capsid reveal that, rather than damaging spike helicity, AT130 enhances the capsid’s ability to recover it. A new conformational state is identified, which can lead to dramatic opening of the intradimer interface and disruption of communication within the spike tip. A novel salt bridge is also discovered, which can mediate contact between the spike tip and fulcrum even in closed conformations, revealing a mechanism of direct communication across these domains. Combined with dynamical network analysis, results describe a connection between the intra- and interdimer interfaces and enable mapping of allostery traversing the entire capsid protein dimer.

scholarly journals The crystal structure of a 250-kDa heterotetrameric particle explains inhibition of sheddase meprin β by endogenous fetuin-B

2021 ◽  
Vol 118 (14) ◽  
pp. e2023839118
Author(s):  
Ulrich Eckhard ◽  
Hagen Körschgen ◽  
Nele von Wiegen ◽  
Walter Stöcker ◽  
F. Xavier Gomis-Rüth
Keyword(s):  
Crystal Structure ◽  
Glycan Structure ◽  
Type I ◽  
Zinc Ions ◽  
Transmembrane Segment ◽  
Protein Inhibitor ◽  
Catalytic Domains ◽  
Endogenous Protein ◽  
Switch Mechanism ◽  
Catalytic Zinc

Meprin β (Mβ) is a multidomain type-I membrane metallopeptidase that sheds membrane-anchored substrates, releasing their soluble forms. Fetuin-B (FB) is its only known endogenous protein inhibitor. Herein, we analyzed the interaction between the ectodomain of Mβ (MβΔC) and FB, which stabilizes the enzyme and inhibits it with subnanomolar affinity. The MβΔC:FB crystal structure reveals a ∼250-kDa, ∼160-Å polyglycosylated heterotetrameric particle with a remarkable glycan structure. Two FB moieties insert like wedges through a “CPDCP trunk” and two hairpins into the respective peptidase catalytic domains, blocking the catalytic zinc ions through an “aspartate switch” mechanism. Uniquely, the active site clefts are obstructed from subsites S4 to S10′, but S1 and S1′ are spared, which prevents cleavage. Modeling of full-length Mβ reveals an EGF-like domain between MβΔC and the transmembrane segment that likely serves as a hinge to transit between membrane-distal and membrane-proximal conformations for inhibition and catalysis, respectively.

scholarly journals An allosteric transport mechanism for the AcrAB-TolC multidrug efflux pump

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Zhao Wang ◽  
Guizhen Fan ◽  
Corey F Hryc ◽  
James N Blaza ◽  
Irina I Serysheva ◽  
...  
Keyword(s):  
Transport Mechanism ◽  
Drug Transport ◽  
Efflux Pump ◽  
Cell Envelope ◽  
Gram Negative Bacteria ◽  
Multidrug Efflux ◽  
Protein Assemblies ◽  
Multidrug Efflux Pump ◽  
Channel Opening ◽  
Activated State

Bacterial efflux pumps confer multidrug resistance by transporting diverse antibiotics from the cell. In Gram-negative bacteria, some of these pumps form multi-protein assemblies that span the cell envelope. Here, we report the near-atomic resolution cryoEM structures of the Escherichia coli AcrAB-TolC multidrug efflux pump in resting and drug transport states, revealing a quaternary structural switch that allosterically couples and synchronizes initial ligand binding with channel opening. Within the transport-activated state, the channel remains open even though the pump cycles through three distinct conformations. Collectively, our data provide a dynamic mechanism for the assembly and operation of the AcrAB-TolC pump.

scholarly journals The High Resolution Crystal Structure of the Human Tumor Suppressor Maspin Reveals a Novel Conformational Switch in the G-helix

2005 ◽  
Vol 280 (23) ◽  
pp. 22356-22364 ◽  
Author(s):  
Ruby H. P. Law ◽  
James A. Irving ◽  
Ashley M. Buckle ◽  
Katya Ruzyla ◽  
Marguerite Buzza ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Tumor Suppressor ◽  
Physiological Role ◽  
Human Tumor ◽  
Salt Bridge ◽  
Structural Data ◽  
Crystal Forms ◽  
Reactive Center ◽  
Α Helix

Maspin is a serpin that acts as a tumor suppressor in a range of human cancers, including tumors of the breast and lung. Maspin is crucial for development, because homozygous loss of the gene is lethal; however, the precise physiological role of the molecule is unclear. To gain insight into the function of human maspin, we have determined its crystal structure in two similar, but non-isomorphous crystal forms, to 2.1- and 2.8-Å resolution, respectively. The structure reveals that maspin adopts the native serpin fold in which the reactive center loop is expelled fully from the A β-sheet, makes minimal contacts with the core of the molecule, and exhibits a high degree of flexibility. A buried salt bridge unique to maspin orthologues causes an unusual bulge in the region around the D and E α-helices, an area of the molecule demonstrated in other serpins to be important for cofactor recognition. Strikingly, the structural data reveal that maspin is able to undergo conformational change in and around the G α-helix, switching between an open and a closed form. This change dictates the electrostatic character of a putative cofactor binding surface and highlights this region as a likely determinant of maspin function. The high resolution crystal structure of maspin provides a detailed molecular framework to elucidate the mechanism of function of this important tumor suppressor.

scholarly journals Latent and activeabPPO4 mushroom tyrosinase cocrystallized with hexatungstotellurate(VI) in a single crystal

2014 ◽  
Vol 70 (9) ◽  
pp. 2301-2315 ◽  
Author(s):  
Stephan Gerhard Mauracher ◽  
Christian Molitor ◽  
Rami Al-Oweini ◽  
Ulrich Kortz ◽  
Annette Rompel
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Agaricus Bisporus ◽  
Crystal Packing ◽  
Active Form ◽  
Activation Mechanism ◽  
Mushroom Tyrosinase ◽  
Polyphenol Oxidases ◽  
Highly Active ◽  
Eukaryotic Organisms

Tyrosinases, bifunctional metalloenzymes, catalyze the oxidation of monophenols ando-diphenols too-quinones, the precursor compounds of the brown-coloured pigment melanin. In eukaryotic organisms, tyrosinases are expressed as latent zymogens that have to be proteolytically cleaved in order to form highly active enzymes. This activation mechanism, known as the tyrosinase maturation process, has scientific and industrial significance with respect to biochemical and technical applications of the enzyme. Here, not only the first crystal structure of the mushroom tyrosinaseabPPO4 is presented in its active form (Ser2–Ser383) and in its 21 kDa heavier latent form (Ser2–Thr545), but furthermore the simultaneous presence of both forms within one single-crystal structure is shown. This allows for a simple approach to investigate the transition between these two forms. IsoformabPPO4 was isolated and extensively purified from the natural source (Agaricus bisporus), which contains a total of six polyphenol oxidases (PPOs). The enzyme formed crystals (diffracting to a resolution of 2.76 Å) owing to the employment of the 6-tungstotellurate(VI) salt (Na6[TeW6O24]·22H2O) as a cocrystallization agent. Two of these disc-shaped Anderson-type polyoxoanions [TeW6O24]6−separate two asymmetric units comprising one crystallographic heterodimer ofabPPO4, thus resulting in very interesting crystal packing.

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