Cryo-EM reconstruction of helical polymers: Beyond the simple cases.

Helices are one of the most frequently encountered symmetries in biological assemblies. Helical symmetry has been exploited in electron microscopic studies as a limited number of filament images, in principle, can provide all the information needed to do a three-dimensional reconstruction of a polymer. Over the past 25 years, three-dimensional reconstructions of helical polymers from cryo-EM images have shifted completely from Fourier-Bessel methods to single-particle approaches.

Crystal structure of glycerol kinase from Trypanosoma cruzi, a potential molecular target in Chagas disease.

Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. It bears a significant global health burden with limited treatment options, thus calling for the development of new and effective drugs. Certain trypanosomal metabolic enzymes have been suggested to be druggable and valid for subsequent inhibition.

Cryo-EM structure of flagellotropic bacteriophage Chi.

The flagellotropic bacteriophage χ (Chi) infects bacteria via the flagellar filament. Despite years of study, its structural architecture remains partly characterized. Through cryo-EM, we unveil χ's nearly complete structure, encompassing capsid, neck, tail, and tail tip.

Atomic structures of naphthalene dipeptide micelles unravel mechanisms of assembly and gelation.

Peptide-based biopolymers have gained increasing attention due to their versatile applications. A naphthalene dipeptide (2NapFF) can form chirality-dependent tubular micelles, leading to supramolecular gels. The precise molecular arrangement within these micelles and the mechanism governing gelation have remained enigmatic.

An extensive disulfide bond network prevents tail contraction in Agrobacterium tumefaciens phage Milano.

A contractile sheath and rigid tube assembly is a widespread apparatus used by bacteriophages, tailocins, and the bacterial type VI secretion system to penetrate cell membranes. In this mechanism, contraction of an external sheath powers the motion of an inner tube through the membrane. The structure, energetics, and mechanism of the machinery imply rigidity and straightness.

Glucose-Triggered Gelation of Supramolecular Peptide Nanocoils with Glucose-Binding Motifs.

Peptide self-assembly is a powerful tool to prepare functional materials at the nanoscale. Often, the resulting materials have high aspect-ratio, with intermolecular β-sheet formation underlying 1D fibrillar structures. Inspired by dynamic structures in nature, peptide self-assembly is increasingly moving toward stimuli-responsive designs wherein assembled structures are formed, altered, or dissipated in response to a specific cue.

Neck and capsid architecture of the robust Agrobacterium phage Milano.

Large gaps exist in our understanding of how bacteriophages, the most abundant biological entities on Earth, assemble and function. The structure of the "neck" region, where the DNA-filled capsid is connected to the host-recognizing tail remains poorly understood. We describe cryo-EM structures of the neck, the neck-capsid and neck-tail junctions, and capsid of the Agrobacterium phage Milano.

The evolution of archaeal flagellar filaments.

Flagellar motility has independently arisen three times during evolution: in bacteria, archaea, and eukaryotes. In prokaryotes, the supercoiled flagellar filaments are composed largely of a single protein, bacterial or archaeal flagellin, although these two proteins are not homologous, while in eukaryotes, the flagellum contains hundreds of proteins. Archaeal flagellin and archaeal type IV pilin are homologous, but how archaeal flagellar filaments (AFFs) and archaeal type IV pili (AT4Ps) diverged is not understood, in part, due to the paucity of structures for AFFs and AT4Ps.

Crystal structure of phycocyanin: implications of light-harvesting and antioxidant properties.

Unlabelled: Phycobiliproteins is a family of chromophore-containing proteins having light-harvesting and antioxidant capacity. The phycocyanin (PC) is a brilliant blue coloured phycobiliprotein, found in rod structure of phycobilisome and has been widely studied for their therapeutic and fluorescent properties. In the present study, the hexameric assembly structure of phycocyanin (Syn-PC) from Sp.

Convergent evolution in the supercoiling of prokaryotic flagellar filaments.

The supercoiling of bacterial and archaeal flagellar filaments is required for motility. Archaeal flagellar filaments have no homology to their bacterial counterparts and are instead homologs of bacterial type IV pili. How these prokaryotic flagellar filaments, each composed of thousands of copies of identical subunits, can form stable supercoils under torsional stress is a fascinating puzzle for which structural insights have been elusive.

Exploring the structural aspects and therapeutic perspectives of cyanobacterial phycobiliproteins.

Phycobiliproteins (PBPs) of cyanobacteria and algae possess unique light harvesting capacity which expand the photosynthetically active region (PAR) and allow them to thrive in extreme niches where higher plants cannot. PBPs of cyanobacteria/algae vary in abundance, types, amino acid composition and in structure as a function of species and the habitat that they grow in. In the present review, the key aspects of structure, stability, and spectral properties of PBPs, and their correlation with ecological niche of cyanobacteria are discussed.

Crystal structure analysis of phycoerythrin from marine cyanobacterium .

Phycoerythrin (PE) is green light-absorbing pigment-protein that assists in efficient light harvesting in cyanobacteria and red-algae. PE in cyanobacteria stays less studied so far as compared to that in red algae. In this study, PE from marine cyanobacteria sp.

Crystal structures of apo- and FAD-bound human peroxisomal acyl-CoA oxidase provide mechanistic basis explaining clinical observations.

Peroxisomal acyl-CoA oxidase 1a (ACOX1a) catalyzes the first and rate-limiting step of fatty acid oxidation, the conversion of acyl-CoAs to 2-trans-enoyl-CoAs. The dysfunction of human ACOX1a (hACOX1a) leads to deterioration of the nervous system manifesting in myeloneuropathy, hypotonia and convulsions. Crystal structures of hACOX1a in apo- and cofactor (FAD)-bound forms were solved at 2.

Distinct sequence and structural feature of trypanosoma malate dehydrogenase.

Glycosomal malate dehydrogenase from Trypanosoma cruzi (tcgMDH) catalyzes the oxidation/reduction of malate/oxaloacetate, a crucial step of the glycolytic process occurring in the glycosome of the human parasite. Inhibition of tcgMDH is considered a druggable trait for the development of trypanocidal drugs. Sequence comparison of MDHs from different organisms revealed a distinct insertion of a prolin rich 9-mer (62-KLPPVPRDP-70) in tcgMDH as compared to other eukaryotic MDHs.

Revisiting high-resolution crystal structure of Phormidium rubidum phycocyanin.

The crystal structure of phycocyanin (pr-PC) isolated from Phormidium rubidum A09DM (P. rubidum) is described at a resolution of 1.17 Å.

Phylogenetic and crystallographic analysis of Nostoc phycocyanin having blue-shifted spectral properties.

The distinct sequence feature and spectral blue-shift (~10 nm) of phycocyanin, isolated from Nostoc sp. R76DM (N-PC), were investigated by phylogenetic and crystallographic analyses. Twelve conserved substitutions in N-PC sequence were found distributed unequally among α- and β-subunit (3 in α- and 9 in β-subunit).

Correction to: Site, trigger, quenching mechanism and recovery of non-photochemical quenching in cyanobacteria: recent updates.

In the original publication, under the subtitle Recovery: fluorescence recovery protein (FRP), paragraph 4 the text section enclosed in quotation marks does not occur in one of the original publications cited (Sluchanko et al. 2017a, b).

Bioproduction and characterization of extracellular melanin-like pigment from industrially polluted metagenomic library equipped Escherichia coli.

To explore the potential genes from the industrially polluted Amlakhadi canal, located in Ankleshwar, Gujarat, India, its community genome was extracted and cloned into E. coli EPI300™-T1 using a fosmid vector (pCC2 FOS™) generating a library of 3,92,000 clones with average size of 40kb of DNA-insert. From this library, the clone DM1 producing brown colored melanin-like pigment was isolated and characterized.

Site, trigger, quenching mechanism and recovery of non-photochemical quenching in cyanobacteria: recent updates.

Cyanobacteria exhibit a novel form of non-photochemical quenching (NPQ) at the level of the phycobilisome. NPQ is a process that protects photosystem II (PSII) from possible highlight-induced photo-damage. Although significant advancement has been made in understanding the NPQ, there are still some missing details.

Antioxidant activity and associated structural attributes of Halomicronema phycoerythrin.

In the present study, blue light absorbing pigment protein phycoerythrin (PE) is purified up to molecular grade purity from marine Halomicronema sp. R31DM. The purification method is based on the use of non-ionic detergent Triton-X 100 in ammonium sulphate precipitation.

An improved crystal structure of C-phycoerythrin from the marine cyanobacterium Phormidium sp. A09DM.

C-Phycoerythrin (PE) from Phormidium sp. A09DM has been crystallized using different conditions and its structure determined to atomic resolution (1.14 Å).

Purification and antioxidant activity of phycocyanin from Synechococcus sp. R42DM isolated from industrially polluted site.

The cyanobacterium Synechococcus sp. R42DM, isolated from an industrially polluted site Vatva, Gujarat, India was recognized to produce phycocyanin (PC) as major phycobiliprotein. In present study, the combinatorial approach of chemical and physical methods i.

Picosecond excitation energy transfer of allophycocyanin studied in solution and in crystals.

Cyanobacteria perform photosynthesis with the use of large light-harvesting antennae called phycobilisomes (PBSs). These hemispherical PBSs contain hundreds of open-chain tetrapyrrole chromophores bound to different peptides, providing an arrangement in which excitation energy is funnelled towards the PBS core from where it can be transferred to photosystem I and/or photosystem II. In the PBS core, many allophycocyanin (APC) trimers are present, red-light-absorbing phycobiliproteins that covalently bind phycocyanobilin (PCB) chromophores.