Light-induced complex formation of bacteriophytochrome RpBphP1 and gene repressor RpPpsR2 probed by SAXS.

Bacteriophytochrome proteins (BphPs) are molecular light switches that enable organisms to adapt to changing light conditions through the control of gene expression. Canonical type 1 BphPs have histidine kinase output domains, but type 3 RpBphP1, in the bacterium Rhodopseudomonas palustris (Rps. palustris), has a C terminal PAS9 domain and a two-helix output sensor (HOS) domain.

Three-dimensional structure of the Rhodobacter sphaeroides RC-LH1-PufX complex: dimerization and quinone channels promoted by PufX.

Reaction center-light harvesting 1 (RC-LH1) complexes are the fundamental units of bacterial photosynthesis, which use solar energy to power the reduction of quinone to quinol prior to the formation of the proton gradient that drives ATP synthesis. The dimeric RC-LH1-PufX complex of Rhodobacter sphaeroides is composed of 64 polypeptides and 128 cofactors, including 56 LH1 bacteriochlorophyll a (BChl a) molecules that surround and donate energy to the two RCs. The 3D structure was determined to 8 Å by X-ray crystallography, and a model was built with constraints provided by electron microscopy (EM), nuclear magnetic resonance (NMR), mass spectrometry (MS), and site-directed mutagenesis.

Evolution of low-light adapted peripheral light-harvesting complexes in strains of Rhodopseudomonas palustris.

Purple bacteria have peripheral light-harvesting (PLH) complexes adapted to high-light (LH2) and low-light (LH3, LH4) growth conditions. The latter two have only been fully characterised in Rhodopseudomonas acidophila 7050 and Rhodopseudomonas palustris CGA009, respectively. It is known that LH4 complexes are expressed under the control of two light sensing bacteriophytochromes (BphPs).

Dimerization properties of the RpBphP2 chromophore-binding domain crystallized by homologue-directed mutagenesis.

Bacteriophytochromes (BphPs) are biliverdin IXα-containing photoreceptors that photoconvert between red (Pr) and far-red (Pfr) absorbing states. BphPs are one half of a two-component system that transmits a light signal to a histidine kinase domain and then to a gene-response regulator. In Rhodopseudomonas palustris, synthesis of a light-harvesting complex (LH4) is controlled by two BphPs (RpBphP2 and RpBphP3).

Structure of a bacteriophytochrome and light-stimulated protomer swapping with a gene repressor.

Phytochromes are photoreceptors in phototropic organisms that respond to light conditions by changing interactions between a response regulator and DNA. Bacterial phytochromes (BphPs) comprise an input photosensory core domain (PCD) and an output transducing domain (OTD). We report the structure of a BphP containing both PCD and the majority of its OTD, and demonstrate interaction with its cognate repressor.

STRU-cloning: a fast, inexpensive and efficient cloning procedure applicable to both small scale and structural genomics size cloning.

We have developed a Single-Tube Restriction-based Ultrafiltration (STRU) cloning procedure that updates traditional ligation-dependent cloning to challenge the newer, faster and more efficient ligation-free techniques and could make it the method of choice. STRU-cloning employs centrifugal filter units with membrane of suitable cut off to remove small unwanted DNA fragments created during restriction of plasmids or PCR products. Heat inactivation, of restriction enzymes, followed by DNA ligation is then performed on the filtrate.

Pigment organization and energy level structure in light-harvesting complex 4: insights from two-dimensional electronic spectroscopy.

Photosynthetic light-harvesting antennae direct energy collected from sunlight to reaction centers with remarkable efficiency and rapidity. Despite their common function, the pigment-protein complexes that make up antenna systems in different types of photosynthetic organisms exhibit a wide variety of structural forms. Some individual organisms express different types of complexes depending on growth conditions.

Laboratory information management system for membrane protein structure initiative--from gene to crystal.

Membrane Protein Structure Initiative (MPSI) exploits laboratory competencies to work collaboratively and distribute work among the different sites. This is possible as protein structure determination requires a series of steps, starting with target selection, through cloning, expression, purification, crystallization and finally structure determination. Distributed sites create a unique set of challenges for integrating and passing on information on the progress of targets.

Small-angle X-ray scattering reveals the solution structure of a bacteriophytochrome in the catalytically active Pr state.

Phytochromes are light-sensing macromolecules that are part of a two component phosphorelay system controlling gene expression. Photoconversion between the Pr and Pfr forms facilitates autophosphorylation of a histidine in the dimerization domain (DHp). We report the low-resolution structure of a bacteriophytochrome (Bph) in the catalytic (CA) Pr form in solution determined by small-angle X-ray scattering (SAXS).

Room to move: crystallizing membrane proteins in swollen lipidic mesophases.

The cubic phase or in meso crystallization method is responsible for almost 40 solved integral membrane protein structures. Most of these are small and compact proteins. A model for how crystals form by the in meso method has been proposed that invokes a transition between mesophases.

A bacteriophytochrome regulates the synthesis of LH4 complexes in Rhodopseudomonas palustris.

The non-sulphur purple bacterium Rhodopseudomonas palustris contains five pucAB genes for peripheral light-harvesting complexes. Bacteria grown under high-light conditions absorb at 800 and 850 nm but in low-light the 850 nm peak is almost absent and LH2 complexes are replaced by LH4. The genome contains six bacteriophytochromes (Bph).

The structure and thermal motion of the B800-850 LH2 complex from Rps.acidophila at 2.0A resolution and 100K: new structural features and functionally relevant motions.

The structure at 100K of integral membrane light-harvesting complex II (LH2) from Rhodopseudomonas acidophila strain 10050 has been refined to 2.0A resolution. The electron density has been significantly improved, compared to the 2.

The 7.5-A electron density and spectroscopic properties of a novel low-light B800 LH2 from Rhodopseudomonas palustris.

A novel low-light (LL) adapted light-harvesting complex II has been isolated from Rhodopseudomonas palustris. Previous work has identified a LL B800-850 complex with a heterogeneous peptide composition and reduced absorption at 850 nm. The work presented here shows the 850 nm absorption to be contamination from a high-light B800-850 complex and that the true LL light-harvesting complex II is a novel B800 complex composed of eight alpha beta(d) peptide pairs that exhibits unique absorption and circular dichroism near infrared spectra.