scholarly journals Structural insights into a dimeric Psb27-photosystem II complex from a cyanobacterium Thermosynechococcus vulcanus

2021 ◽  
Vol 118 (5) ◽  
pp. e2018053118
Author(s):  
Guoqiang Huang ◽  
Yanan Xiao ◽  
Xiong Pi ◽  
Liang Zhao ◽  
Qingjun Zhu ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Conformational Changes ◽  
Water Oxidation ◽  
Structural Information ◽  
Regulation Mechanism ◽  
Loop Region ◽  
Luminal Side ◽  
Assembly Factor ◽  
Pigment Protein Complex ◽  
Structural Insights

Photosystem II (PSII) is a multisubunit pigment-protein complex and catalyzes light-driven water oxidation, leading to the conversion of light energy into chemical energy and the release of molecular oxygen. Psb27 is a small thylakoid lumen-localized protein known to serve as an assembly factor for the biogenesis and repair of the PSII complex. The exact location and binding fashion of Psb27 in the intermediate PSII remain elusive. Here, we report the structure of a dimeric Psb27-PSII complex purified from a psbV deletion mutant (ΔPsbV) of the cyanobacterium Thermosynechococcus vulcanus, solved by cryo-electron microscopy. Our structure showed that Psb27 is associated with CP43 at the luminal side, with specific interactions formed between Helix 2 and Helix 3 of Psb27 and a loop region between Helix 3 and Helix 4 of CP43 (loop C) as well as the large, lumen-exposed and hydrophilic E-loop of CP43. The binding of Psb27 imposes some conflicts with the N-terminal region of PsbO and also induces some conformational changes in CP43, CP47, and D2. This makes PsbO unable to bind in the Psb27-PSII. Conformational changes also occurred in D1, PsbE, PsbF, and PsbZ; this, together with the conformational changes occurred in CP43, CP47, and D2, may prevent the binding of PsbU and induce dissociation of PsbJ. This structural information provides important insights into the regulation mechanism of Psb27 in the biogenesis and repair of PSII.

scholarly journals The P1 and P2 helices of the Guanidinium-II riboswitch interact in a ligand-dependent manner

2021 ◽  
Author(s):  
Christin Fuks ◽  
Sebastian Falkner ◽  
Nadine Schwierz ◽  
Martin Hengesbach
Keyword(s):  
Single Molecule ◽  
Conformational Changes ◽  
Environmental Conditions ◽  
Structural Information ◽  
Coarse Grained ◽  
Regulation Mechanism ◽  
Dependent Manner ◽  
Loop Formation ◽  
Coarse Grained Simulations ◽  
Kissing Loop

ABSTRACTRiboswitch RNAs regulate gene expression by conformational changes induced by environmental conditions and specific ligand binding. The guanidine-II riboswitch is proposed to bind the small molecule guanidinium and to subsequently form a kissing loop interaction between the P1 and P2 hairpins. While an interaction was shown for isolated hairpins in crystallization and EPR experiments, an intrastrand kissing loop formation has not been demonstrated. Here, we report the first evidence of this interaction in cis in a ligand and Mg2+ dependent manner. Using single-molecule FRET spectroscopy and detailed structural information from coarse-grained simulations, we observe and characterize three interconvertible states representing an open and kissing loop conformation as well as a novel Mg2+ dependent state for the guanidine-II riboswitch from E. coli. The results further substantiate the proposed switching mechanism and provide detailed insight into the regulation mechanism for the guanidine-II riboswitch class. Combining single molecule experiments and coarse-grained simulations therefore provides a promising perspective in resolving the conformational changes induced by environmental conditions and to yield molecular insights into RNA regulation.

scholarly journals Probing the CD Lumenal Loop Region of the D2 Protein of Photosystem II in Synechocystis sp. Strain PCC 6803 by Combinatorial Mutagenesis

2000 ◽  
Vol 182 (9) ◽  
pp. 2453-2460 ◽  
Author(s):  
Anna T. Keilty ◽  
Svetlana Y. Ermakova-Gerdes ◽  
Wim F. J. Vermaas
Keyword(s):  
Photosystem Ii ◽  
Structural Information ◽  
Site Directed Mutagenesis ◽  
Functional Requirements ◽  
Coding Region ◽  
Functional Roles ◽  
Loop Region ◽  
Combinatorial Mutagenesis ◽  
D2 Protein ◽  
Pcc 6803

ABSTRACT The CD lumenal loop region of the photosystem II reaction center protein D2 contains residues involved in oxygen evolution. Since detailed structural information about this region is unavailable, an M13-based combinatorial mutagenesis approach was used to investigate structure-function relationships in this vital region of D2 inSynechocystis sp. strain PCC 6803. The CD loop coding region contains close to 100 nucleotides, and for effective mutagenesis, it was subdivided into four regions of seven to eight codons. A gain-of-function selection protocol was employed such that all mutants that were selected contained a functional D2 protein. In this way, conservation patterns of residues along with numbers and types of amino acid substitutions accommodated at each position for each set of mutants would indicate which residues in the CD loop may play important structural and functional roles. Results of this study have substantiated the importance of residues previously studied by site-directed mutagenesis such as Arg180 and His189 and have identified other previously unremarkable residues in the CD loop (such as Ser166, Phe169, and Ala170) that cannot be replaced by many other residues. In addition, the pliability of the CD loop was further tested using deletion and D1-D2 substitution constructs in M13. This showed that the length of the loop was important to its function, and in two cases, D2 could accommodate homologous sequences from D1, which forms a heterodimer with D2 in photosystem II, but not the other way around. This study of the CD loop in D2 provides valuable clues regarding the structural and functional requirements of the region.

Crystal structures of Magnaporthe oryzae trehalose-6-phosphate synthase (MoTps1) suggest a model for catalytic process of Tps1

2019 ◽  
Vol 476 (21) ◽  
pp. 3227-3240 ◽  
Author(s):  
Shanshan Wang ◽  
Yanxiang Zhao ◽  
Long Yi ◽  
Minghe Shen ◽  
Chao Wang ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Conformational Changes ◽  
Magnaporthe Oryzae ◽  
Structural Information ◽  
Complex Structure ◽  
Critical Role ◽  
Catalytic Process ◽  
Structural Basis ◽  
Salt Bridges ◽  
Terminal Domain

Trehalose-6-phosphate (T6P) synthase (Tps1) catalyzes the formation of T6P from UDP-glucose (UDPG) (or GDPG, etc.) and glucose-6-phosphate (G6P), and structural basis of this process has not been well studied. MoTps1 (Magnaporthe oryzae Tps1) plays a critical role in carbon and nitrogen metabolism, but its structural information is unknown. Here we present the crystal structures of MoTps1 apo, binary (with UDPG) and ternary (with UDPG/G6P or UDP/T6P) complexes. MoTps1 consists of two modified Rossmann-fold domains and a catalytic center in-between. Unlike Escherichia coli OtsA (EcOtsA, the Tps1 of E. coli), MoTps1 exists as a mixture of monomer, dimer, and oligomer in solution. Inter-chain salt bridges, which are not fully conserved in EcOtsA, play primary roles in MoTps1 oligomerization. Binding of UDPG by MoTps1 C-terminal domain modifies the substrate pocket of MoTps1. In the MoTps1 ternary complex structure, UDP and T6P, the products of UDPG and G6P, are detected, and substantial conformational rearrangements of N-terminal domain, including structural reshuffling (β3–β4 loop to α0 helix) and movement of a ‘shift region' towards the catalytic centre, are observed. These conformational changes render MoTps1 to a ‘closed' state compared with its ‘open' state in apo or UDPG complex structures. By solving the EcOtsA apo structure, we confirmed that similar ligand binding induced conformational changes also exist in EcOtsA, although no structural reshuffling involved. Based on our research and previous studies, we present a model for the catalytic process of Tps1. Our research provides novel information on MoTps1, Tps1 family, and structure-based antifungal drug design.

Investigating the dynamic nature of the ABC transporters: ABCB1 and MsbA as examples for the potential synergies of MD theory and EPR applications

2015 ◽  
Vol 43 (5) ◽  
pp. 1023-1032 ◽  
Author(s):  
Thomas Stockner ◽  
Anna Mullen ◽  
Fraser MacMillan
Keyword(s):  
Crystal Structures ◽  
Conformational Changes ◽  
Abc Transporters ◽  
Epr Spectroscopy ◽  
Structural Information ◽  
Dynamic Properties ◽  
Molecular System ◽  
Synergistic Effects ◽  
Md Simulations ◽  
Substrate Spectrum

ABC transporters are primary active transporters found in all kingdoms of life. Human multidrug resistance transporter ABCB1, or P-glycoprotein, has an extremely broad substrate spectrum and confers resistance against chemotherapy drug treatment in cancer cells. The bacterial ABC transporter MsbA is a lipid A flippase and a homolog to the human ABCB1 transporter, with which it partially shares its substrate spectrum. Crystal structures of MsbA and ABCB1 have been solved in multiple conformations, providing a glimpse into the possible conformational changes the transporter could be going through during the transport cycle. Crystal structures are inherently static, while a dynamic picture of the transporter in motion is needed for a complete understanding of transporter function. Molecular dynamics (MD) simulations and electron paramagnetic resonance (EPR) spectroscopy can provide structural information on ABC transporters, but the strength of these two methods lies in the potential to characterise the dynamic regime of these transporters. Information from the two methods is quite complementary. MD simulations provide an all atom dynamic picture of the time evolution of the molecular system, though with a narrow time window. EPR spectroscopy can probe structural, environmental and dynamic properties of the transporter in several time regimes, but only through the attachment sites of an exogenous spin label. In this review the synergistic effects that can be achieved by combining the two methods are highlighted, and a brief methodological background is also presented.

Conformational changes of the intermediate of the S2 to S3 transition in photosystem II

2011 ◽  
Vol 104 (1-2) ◽  
pp. 72-79 ◽  
Author(s):  
Maria Chrysina ◽  
Georgia Zahariou ◽  
Yiannis Sanakis ◽  
Nikolaos Ioannidis ◽  
Vasili Petrouleas
Keyword(s):  
Photosystem Ii ◽  
Conformational Changes

Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction

1998 ◽  
Vol 53 (9-10) ◽  
pp. 849-856
Author(s):  
Sujata R. Mishra ◽  
Surendra Chandra Sabat
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Water Oxidation ◽  
Electron Flow ◽  
Hydrilla Verticillata ◽  
Transport Activity ◽  
Low Salt ◽  
Electron Transport Activity ◽  
Stimulation Of

Stimulatory effect of divalent cations like calcium (Ca2+) and magnesium (Mg2+) was investigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (NH2OH) - or alkaline Tris - washed thylakoid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimulation of electron transport activity was found. The apparent Km of Ca2+ dependent stimulation of electron flow from H2O (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimulation of electron transport activity in NH2OH - or Tris - washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with NH2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in NH2OH - or Tris - washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Yz and reaction center of photosystem II.

The S2 to S3 transition for water oxidation in PSII (photosystem II), revisited

2018 ◽  
Vol 20 (35) ◽  
pp. 22926-22931 ◽  
Author(s):  
Per E. M. Siegbahn
Keyword(s):  
Photosystem Ii ◽  
Water Oxidation ◽  
Light Flash

The formation of O2 from water requires four transitions, each one after the absorption of one light flash.

Sign in / Sign up

Export Citation Format

Share Document