25 research outputs found
Triplet Charge Recombination in Heliobacterial Reaction Centers Does Not Produce a Spin-Polarized EPR Spectrum
No full textStructural Characterization of a Synthetic Tandem-Domain Bacterial Microcompartment Shell Protein Capable of Forming Icosahedral Shell Assemblies
No full textBacterial
microcompartments are subcellular compartments found
in many prokaryotes; they consist of a protein shell that encapsulates
enzymes that perform a variety of functions. The shell protects the
cell from potentially toxic intermediates and colocalizes enzymes
for higher efficiency. Accordingly, it is of considerable interest
for biotechnological applications. We have previously structurally
characterized an intact 40 nm shell comprising three different types
of proteins. One of those proteins, BMC-H, forms a cyclic hexamer;
here we have engineered a synthetic protein that consists of a tandem
duplication of BMC-H connected by a short linker. The synthetic protein
forms cyclic trimers that self-assemble to form a smaller (25 nm)
icosahedral shell with gaps at the pentamer positions. When coexpressed in vivo with the pentamer fused to an affinity tag we can
purify complete icosahedral shells. This engineered shell protein
constitutes a minimal shell system to study permeability; reducing
symmetry from 6- to 3-fold will allow for finer control of the pore
environment. We have determined a crystal structure of this shell
to guide rational engineering of this microcompartment shell for biotechnological
applications
Heterologous Assembly of Pleomorphic Bacterial Microcompartment Shell Architectures Spanning the Nano‐ to Microscale
No full textMany bacteria use protein-based organelles known as bacterial microcompartments (BMCs) to organize and sequester sequential enzymatic reactions. Regardless of their specialized metabolic function, all BMCs are delimited by a shell made of multiple structurally redundant, yet functionally diverse, hexameric (BMC-H), pseudohexameric/trimeric (BMC-T), or pentameric (BMC-P) shell protein paralogs. When expressed without their native cargo, shell proteins have been shown to self-assemble into 2D sheets, open-ended nanotubes, and closed shells of ≈40 nm diameter that are being developed as scaffolds and nanocontainers for applications in biotechnology. Here, by leveraging a strategy for affinity-based purification, it is demonstrated that a wide range of empty synthetic shells, many differing in end-cap structures, can be derived from a glycyl radical enzyme-associated microcompartment. The range of pleomorphic shells observed, which span ≈2 orders of magnitude in size from ≈25 nm to ≈1.8 µm, reveal the remarkable plasticity of BMC-based biomaterials. In addition, new capped nanotube and nanocone morphologies are observed that are consistent with a multicomponent geometric model in which architectural principles are shared among asymmetric carbon, viral protein, and BMC-based structures
Heterologous Assembly of Pleomorphic Bacterial Microcompartment Shell Architectures Spanning the Nano‐ to Microscale
No full textStructure of a symmetric photosynthetic reaction center–photosystem
No full textA homodimeric complex for anaerobic photosynthesis
In plants, algae, and cyanobacteria, large molecular complexes—photosystems I and II—convert light energy into chemical energy, releasing oxygen as a by-product. This oxygenic photosynthesis is critical for maintaining Earth's atmospheric oxygen. At their cores, photosystems I and II contain a heterodimeric reaction center. Reaction centers evolved in an atmosphere lacking oxygen, and the ancestral complex was likely homodimeric, encoded by a single gene. Gisriel
et al.
describe the structure of a homodimeric reaction center from an anoxygenic photosynthetic bacterium. The structure shows perfect symmetry of the light-collecting antennae and elucidates the electron transfer chain.
Science
, this issue p.
1021
</jats:p
The effect of bacteriochlorophyll g oxidation on energy and electron transfer in reaction centers from Heliobacterium modesticaldum
No full textElectron transfer from the A1A and A1B sites to a tethered Pt nanoparticle requires the FeS clusters for suppression of the recombination channel
No full textToward a glycyl radical enzyme containing synthetic bacterial microcompartment to produce pyruvate from formate and acetate
No full textRecommended from our members
Functionalization of Bacterial Microcompartment Shell Proteins With Covalently Attached Heme
No full textHeme is a versatile redox cofactor that has considerable potential for synthetic biology and bioelectronic applications. The capacity to functionalize non-heme-binding proteins with covalently bound heme moieties in vivo could expand the variety of bioelectronic materials, particularly if hemes could be attached at defined locations so as to facilitate position-sensitive processes like electron transfer. In this study, we utilized the cytochrome maturation system I to develop a simple approach that enables incorporation of hemes into the backbone of target proteins in vivo. We tested our methodology by targeting the self-assembling bacterial microcompartment shell proteins, and inserting functional hemes at multiple locations in the protein backbone. We found substitution of three amino acids on the target proteins promoted heme attachment with high occupancy. Spectroscopic measurements suggested these modified proteins covalently bind low-spin hemes, with relative low redox midpoint potentials (about -210 mV vs. SHE). Heme-modified shell proteins partially retained their self-assembly properties, including the capacity to hexamerize, and form inter-hexamer attachments. Heme-bound shell proteins demonstrated the capacity to integrate into higher-order shell assemblies, however, the structural features of these macromolecular complexes was sometimes altered. Altogether, we report a versatile strategy for generating electron-conductive cytochromes from structurally-defined proteins, and provide design considerations on how heme incorporation may interface with native assembly properties in engineered proteins
Functionalization of Bacterial Microcompartment Shell Proteins With Covalently Attached Heme
No full text
