Rapid-Scan Fourier Transform Infrared Monitoring of the Photoactivation Process in Cyanobacterial Photosystem II.

The catalytic site of photosynthetic water oxidation, the MnCaO cluster, in photosystem II (PSII) is known to be formed by a light-induced process called photoactivation. However, details of its molecular mechanism remain unresolved. In this study, we monitored the photoactivation process in cyanobacterial PSII using rapid-scan, time-resolved Fourier transform infrared (FTIR) spectroscopy.

Post-translational amino acid conversion in photosystem II as a possible origin of photosynthetic oxygen evolution.

Photosynthetic oxygen evolution is performed at the Mn cluster in photosystem II (PSII). The advent of this reaction on ancient Earth changed its environment by generating an oxygenic atmosphere. However, how oxygen evolution originated during the PSII evolution remains unknown.

Role of the O4 Channel in Photosynthetic Water Oxidation as Revealed by Fourier Transform Infrared Difference and Time-Resolved Infrared Analysis of the D1-S169A Mutant.

Photosynthetic water oxidation takes place at the MnCaO cluster in photosystem II. Although the atomic structures of its intermediates called S states have recently been reported, the catalytic mechanism of water oxidation has not been well understood. Here, to investigate the involvement of the O4 site of the MnCaO cluster and a water channel from O4 in the water oxidation reaction, we examined the effects of D1-S169A mutation, which perturbs the interaction of a water molecule hydrogen-bonded with O4, by thermoluminescence (TL), Fourier transform infrared (FTIR) difference, and time-resolved infrared (TRIR) measurements.

Fourier transform infrared and mass spectrometry analyses of a site-directed mutant of D1-Asp170 as a ligand to the water-oxidizing MnCaO cluster in photosystem II.

The MnCaO cluster, the catalytic center of water oxidation in photosystem II (PSII), is coordinated by six carboxylate and one imidazole ligands. The roles of these ligands in the water oxidation mechanism remain largely unknown. In this study, we constructed a D1-D170H mutant, in which the Asp ligand bridging Mn and Ca ions was replaced with His, in the cyanobacterium Synechocystis sp.

Crystal structure of Cruxrhodopsin-3 from Haloarcula vallismortis.

Cruxrhodopsin-3 (cR3), a retinylidene protein found in the claret membrane of Haloarcula vallismortis, functions as a light-driven proton pump. In this study, the membrane fusion method was applied to crystallize cR3 into a crystal belonging to space group P321. Diffraction data at 2.

Gene orders in the upstream of 16S rRNA genes divide genera of the family Halobacteriaceae into two groups.

In many prokaryotic species, 16S rRNA genes are present in multiple copies, and their sequences in general do not differ significantly owing to concerted evolution. At the time of writing, the genus Haloarcula of the family Halobacteriaceae comprises nine species with validly published names, all of which possess two to four highly heterogeneous 16S rRNA genes. Existence of multiple heterogeneous 16S rRNA genes makes it difficult to reconstruct a biological phylogenetic tree using their sequence data.

A photochromic photoreceptor from a eubacterium.

Sensory rhodopsin I (SRI) is one of the most interesting photo- sensory receptors because of its function in using the photochromic reaction to mediate opposing signals which depend on the color of light. It was initially thought that SRI exists only in the archaea, but we recently reported for the first time a newly functional SRI from a eubacterium, Salinibacter ruber (SrSRI). The amino acid sequence of SrSRI shows 43% identity with the well-known SRI (HsSRI) and contains most of the amino acid residues identified as necessary for SRI function.

Functionally important structural elements of the cyanobacterial clock-related protein Pex.

Pex, a clock-related protein involved in the input pathway of the cyanobacterial circadian clock system, suppresses the expression of clock gene kaiA and lengthens the circadian period. Here, we determined the crystal structure of Anabaena Pex (AnaPex; Anabaena sp. strain PCC 7120) and Synechococcus Pex (SynPex; Synechococcus sp.

Salinibacter sensory rhodopsin: sensory rhodopsin I-like protein from a eubacterium.

Halobacterium salinarum sensory rhodopsin I (HsSRI), a dual receptor regulating both negative and positive phototaxis in haloarchaea, transmits light signals through changes in protein-protein interactions with its transducer, halobacterial transducer protein I (HtrI). Haloarchaea also have another sensor pigment, sensory rhodopsin II (SRII), which functions as a receptor regulating negative phototaxis. Compared with HsSRI, the signal relay mechanism of SRII is well characterized because SRII from Natronomonus pharaonis (NpSRII) is much more stable than HsSRI and HsSRII, especially in dilute salt solutions and is much more resistant to detergents.