Structure And Function Of The FMO Protein From The Photosynthetic Green Sulfur Bacteria

The Fenna-Matthews-Olson: FMO) bacteriochlorophyll a protein has served as a model antenna system for understanding pigment-protein interaction and the energy transfer mechanism. The FMO protein has been extensively studied by a wide range of spectroscopic and theoretical techniques due to its stability, spectral resolution of pigments, water-soluble nature and availability of high-resolution structural information. A new 1.3 Å FMO structure: PDB: 3EOJ) revealed an 8th pigment at the monomer connection region with partial occupancy. To understand the nature and stoichiometry of this new pigment, the molecular weight of the whole FMO complex was measured by the recently developed mass spectrometry: MS) technique called native spray MS. The first non-natural FMO complex was generated by replacing the phytol tail of BChl a with geranylgeraniol. The recently discovered sixth phylum of photosynthetic species - the Candidatus Chloracidobacterium thermophilum: Cab), also contains the FMO protein, which is significantly divergent from the FMO found in green sulfur bacteria: GSB). This FMO has two distinct structural regions different from the FMOs from GSB and also shows distinct spectral properties. The collection of these different FMO complexes has greatly facilitated our understanding of this protein. The FMO connects the chlorosome to the reaction center in the cytoplasmic membrane and functionally forms a bridge to transfer the excitation energy. The orientation of the FMO protein on the membrane in vivo was revealed by chemical labeling and MS5. The orientational information places the newly discovered 8th pigment near the chlorosome, and it is proposed to serve as an energy transfer intermediate between the chlorosome and the rest of the FMO protein. The detailed interaction between the FMO protein and the baseplate: CsmA) protein was studied by hydrogen/deuterium exchange coupled with MS. The identified binding region first confirms the FMO orientation on the membrane; secondly this region is located at one of the two structurally different regions on the Cab-FMO protein, and the highly conserved region in the baseplate of GSB is not conserved in that of Cab

A secretory kinase complex regulates extracellular protein phosphorylation.

Although numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation

Poly[octa­aquadi-μ-phosphato-trinickel(II)]. Corrigendum

Corrigendum to Acta Cryst. (2008), E64, m259

Three dimensional spider-web-like superconducting filamentary paths in KxFe2−ySe2K_xFe_{2-y}Se_2 single crystals

Since the discovery of high temperature superconductivity in F-doped LaFeAsO, many new iron based superconductors with different structures have been fabricated2. The observation of superconductivity at about 32 K in KxFe2-ySe2 with the iso-structure of the FeAs-based 122 superconductors was a surprise and immediately stimulated the interests because the band structure calculation8 predicted the absence of the hole pocket which was supposed to be necessary for the theoretical picture of S+- pairing. Soon later, it was found that the material may separate into the insulating antiferromagnetic K2Fe4Se5 phase and the superconducting phase. It remains unresolved that how these two phases coexist and what is the parent phase for superconductivity. In this study we use different quenching processes to produce the target samples with distinct microstructures, and apply multiple measuring techniques to reveal a close relationship between the microstructures and the global appearance of superconductivity. In addition, we clearly illustrate three dimensional spider-web-like superconducting filamentary paths, and for the first time propose that the superconducting phase may originate from a state with one vacancy in every eight Fe-sites with the root8*root10 parallelogram structure.Comment: 22 pages, 7 figure

Pressure Induced Suppression to the Valence Change Transition in EuPdAs

By applying a hydrostatic pressure, we have successfully suppressed the valence change transition in EuPdAs. The studied compound EuPdAs crystallizes in a P63/mmc space group. Through resistivity and magnetic susceptibility measurements, we find that EuPdAs shows a phase transition at 180 K and another transition below 10 K at ambient pressure, as was reported before. The overall transport and magnetic behavior is to some extent similar to that of the parent phase of iron based superconductors. With application of a hydrostatic pressure, the transition at 180 K is sensitively suppressed with a pressure as low as 0.48 GPa. However, superconductivity has not been induced with pressure up to 1.90 GPa