Probing the Dual Role of Ca in the LH1-RC Complex by Constructing and Analyzing Ca-Bound and Ca-Free LH1 Complexes.

The genome of the mildly thermophilic hot spring purple sulfur bacterium, (.) , contains a multigene family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous light-harvesting 1 (LH1) complex. The LH1, therefore, offers a unique model for studying an intermediate phenotype between phototrophic thermophilic and mesophilic bacteria, particularly regarding their LH1 transition and moderately enhanced thermal stability.

A Native LH1-RC-HiPIP Supercomplex from an Extremophilic Phototroph.

Halorhodospira (Hlr.) halophila strain BN9622 is an extremely halophilic and alkaliphilic purple phototrophic bacterium and has been widely used as a model for exploring the osmoadaptive and photosynthetic strategies employed by phototrophic extreme halophiles that enable them to thrive in hypersaline environments. Here we present the cryo-EM structures of (1) a unique native Hlr.

Insights into the divergence of the photosynthetic LH1 complex obtained from structural analysis of the unusual photocomplexes of Roseospirillum parvum.

Purple phototrophic bacteria produce two kinds of light-harvesting complexes that function to capture and transmit solar energy: the core antenna (LH1) and the peripheral antenna (LH2). The apoproteins of these antennas, encoded respectively by the genes pufBA and pucBA within and outside the photosynthetic gene cluster, respectively, exhibit conserved amino acid sequences and structural topologies suggesting they were derived from a shared ancestor. Here we present the structures of two photosynthetic complexes from Roseospirillum (Rss.

Architecture of the spinach plastid-encoded RNA polymerase.

The plastid-encoded RNA polymerase serves as the principal transcription machinery within chloroplasts, transcribing over 80% of all primary plastid transcripts. This polymerase consists of a prokaryotic-like core enzyme known as the plastid-encoded RNA polymerase core, and is supplemented by newly evolved associated proteins known as PAPs. However, the architecture of the plastid-encoded RNA polymerase and the possible functions of PAPs remain unknown.

Unleashing the Power of Evolution in Xylanase Engineering: Investigating the Role of Distal Mutation Regulation.

The drive to enhance enzyme performance in industrial applications frequently clashes with the practical limitations of exhaustive experimental screening, underscoring the urgency for more refined and strategic methodologies in enzyme engineering. In this study, xylanase Xyl-1 was used as the model, coupling evolutionary insights with energy functions to obtain theoretical potential mutants, which were subsequently validated experimentally. We observed that mutations in the nonloop region primarily aimed at enhancing stability and also encountered selective pressure for activity.

Molecular structure and characterization of the Thermochromatium tepidum light-harvesting 1 photocomplex produced in a foreign host.

Purple phototrophic bacteria possess light-harvesting 1 and reaction center (LH1-RC) core complexes that play a key role in converting solar energy to chemical energy. High-resolution structures of LH1-RC and RC complexes have been intensively studied and have yielded critical insight into the architecture and interactions of their proteins, pigments, and cofactors. Nevertheless, a detailed picture of the structure and assembly of LH1-only complexes is lacking due to the intimate association between LH1 and the RC.

Energy Transfer and Exciton Relaxation in B880-B800-RC Complex through Two-Dimensional Electronic Spectroscopy.

The light-harvesting (LH) and reaction center (RC) core complex of purple bacterium , B880-B800-RC, are different from those of the typical photosynthetic unit, (B850-B800)-B880-RC. To investigate the excitation flowing dynamics in this unique complex, two-dimensional electronic spectroscopy is employed. The obtained time constants for the exciton relaxation in B880, exciton relaxation in B800, B800 → B880 energy transfer (EET), and B880 → closed RC EET are 43 fs, 177 fs, 1.

Light-Quality-Adapted Carotenoid Photoprotection in the Photosystem of .

The photosystem of filamentous anoxygenic phototroph (.) comprises a light-harvesting (LH) complex encircling a reaction center (RC), which intensely absorbs blue-green light by carotenoid (Car) and near-infrared light by bacteriochlorophyll (BChl). To explore the influence of light quality (color) on the photosynthetic activity, we compared the pigment compositions and triplet excitation dynamics of the LH-RCs from .

High-resolution structure and biochemical properties of the LH1-RC photocomplex from the model purple sulfur bacterium, Allochromatium vinosum.

The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc.

Structures and organizations of PSI-AcpPCI supercomplexes from red tidal and coral symbiotic photosynthetic dinoflagellates.

Marine photosynthetic dinoflagellates are a group of successful phytoplankton that can form red tides in the ocean and also symbiosis with corals. These features are closely related to the photosynthetic properties of dinoflagellates. We report here three structures of photosystem I (PSI)-chlorophylls (Chls) /-peridinin protein complex (PSI-AcpPCI) from two species of dinoflagellates by single-particle cryoelectron microscopy.

Structural insights into photosystem II supercomplex and trimeric FCP antennae of a centric diatom Cyclotella meneghiniana.

Diatoms are dominant marine algae and contribute around a quarter of global primary productivity, the success of which is largely attributed to their photosynthetic capacity aided by specific fucoxanthin chlorophyll-binding proteins (FCPs) to enhance the blue-green light absorption under water. We purified a photosystem II (PSII)-FCPII supercomplex and a trimeric FCP from Cyclotella meneghiniana (Cm) and solved their structures by cryo-electron microscopy (cryo-EM). The structures reveal detailed organizations of monomeric, dimeric and trimeric FCP antennae, as well as distinct assemblies of Lhcx6_1 and dimeric FCPII-H in PSII core.

Carotenoid-Mediated Long-Range Energy Transfer in the Light Harvesting-Reaction Center Complex from Photosynthetic Bacterium .

The light harvesting-reaction center complex (LH-RC) of binds bacteriochlorophylls (BChls ), B800 and B880, absorbing around 800 and 880 nm, respectively. We comparatively investigated the interband excitation energy transfer (EET) dynamics of the wild-type LH-RC (wtLH-RC) of . and its carotenoid (Car)-less mutant (m-LH-RC) and found that Car can boost the B800 → B880 EET rate from (2.

Propeptide-Mediated Allosteric Regulation of Xylanase Xyl-1: An Integrated Experimental and Computational Analysis.

Most GH11 family endo-β-1,4-xylanases contain a propeptide region linked to the N-terminal region. The mechanistic basis of this region harboring key regulation information for enzyme function, however, remains poorly understood. We reported an investigation on the allosteric regulation mechanism of the propeptide based on biochemical characterization, molecular dynamics simulations, and evolutionary analysis.

New insights on the photocomplex of Roseiflexus castenholzii revealed from comparisons of native and carotenoid-depleted complexes.

In wild-type phototrophic organisms, carotenoids (Crts) are primarily packed into specific pigment-protein complexes along with (Bacterio)chlorophylls and play important roles in the photosynthesis. Diphenylamine (DPA) inhibits carotenogenesis but not phototrophic growth of anoxygenic phototrophs and eliminates virtually all Crts from photocomplexes. To investigate the effect of Crts on assembly of the reaction center-light-harvesting (RC-LH) complex from the filamentous anoxygenic phototroph Roseiflexus (Rfl.

An aminocaproic acid-grafted chitosan derivative with superior antibacterial and hemostatic properties for the prevention of secondary bleeding.

Uncontrolled bleeding is one of the leading causes of human mortality. Existing hemostatic materials or techniques cannot meet the clinical requirements for safe and effective hemostasis. The development of novel hemostatic materials has always been of great interest.

Au Nanoparticles/HfO₂/Fully Depleted Silicon-on-Insulator MOSFET Enabled Rapid Detection of Zeptomole COVID-19 Gene With Electrostatic Enrichment Process.

In this work, a novel sensing structure based on Au nanoparticles/HfO2/fully depleted silicon-on-insulator (AuNPs/HfO2/FDSOI) MOSFET is fabricated. Using such a planar double gate MOSFET, the electrostatic enrichment (ESE) process is proposed for the ultrasensitive and rapid detection of the coronavirus disease 2019 (COVID-19) ORF1ab gene. The back-gate (BG) bias can induce the required electric field that enables the ESE process in the testing liquid analyte with indirect contact with the top-Si layer.

An LH1-RC photocomplex from an extremophilic phototroph provides insight into origins of two photosynthesis proteins.

Rhodopila globiformis is the most acidophilic of anaerobic purple phototrophs, growing optimally in culture at pH 5. Here we present a cryo-EM structure of the light-harvesting 1-reaction center (LH1-RC) complex from Rhodopila globiformis at 2.24 Å resolution.

A Ca-binding motif underlies the unusual properties of certain photosynthetic bacterial core light-harvesting complexes.

The mildly thermophilic purple phototrophic bacterium Allochromatium tepidum provides a unique model for investigating various intermediate phenotypes observed between those of thermophilic and mesophilic counterparts. The core light-harvesting (LH1) complex from A. tepidum exhibits an absorption maximum at 890 nm and mildly enhanced thermostability, both of which are Ca-dependent.

Carotenoid Single-Molecular Singlet Fission and the Photoprotection of a Bacteriochlorophyll -Type Core Light-Harvesting Antenna.

Carotenoid (Car) in photosynthesis plays the major roles of accessary light harvesting and photoprotection, and the underlying structure-function relationship attracts continuing research interests. We have attempted to explore the dynamics of Car triplet excitation (Car*) in the bacteriochlorophyll (BChl )-type light harvesting reaction center complex (LH1-RC) of photosynthetic bacterium . We show that the LH1 antenna binds a single Car that was identified as a lycopene derivative.

Asymmetric structure of the native Rhodobacter sphaeroides dimeric LH1-RC complex.

Rhodobacter sphaeroides is a model organism in bacterial photosynthesis, and its light-harvesting-reaction center (LH1-RC) complex contains both dimeric and monomeric forms. Here we present cryo-EM structures of the native LH1-RC dimer and an LH1-RC monomer lacking protein-U (ΔU). The native dimer reveals several asymmetric features including the arrangement of its two monomeric components, the structural integrity of protein-U, the overall organization of LH1, and rigidities of the proteins and pigments.

A previously unrecognized membrane protein in the Rhodobacter sphaeroides LH1-RC photocomplex.

Rhodobacter (Rba.) sphaeroides is the most widely used model organism in bacterial photosynthesis. The light-harvesting-reaction center (LH1-RC) core complex of this purple phototroph is characterized by the co-existence of monomeric and dimeric forms, the presence of the protein PufX, and approximately two carotenoids per LH1 αβ-polypeptides.