Satoru Murakami

RESTRUCTURING OF THE BLEOMYCIN METAL CORE. NOVEL OXYGEN-ACTIVATING LIGANDS WITH SYMMETRIZED STRUCTURE

Abstract Novel ligands having symmetrized coordination environment consisting of two histidine units and a pyridine are prepared. Oxygen activating efficiency of the iron complexes of the synthetic ligands increases by introducing electron donating substituent into the pyridine ring.

Three-dimensional structure of the prolamellar body in squash etioplasts

SummaryHigh resolution scanning electron microscopy revealed that the basic unit of the paracrystalline network in squash prolamellar body is a tetrapodal structure, which has four short tubular arms meeting at one point with equal angle. Fractured faces of the prolamellar bodies displayed three lattice forms; hexagonal, square and zigzag (distorted hexagonal) lattices. Tilting observations of the ultrathin sections, together with scanning electron microscope observations, showed that the paracrystalline tubular network in the squash prolamellar body is of zincblende-type. A pentagonal configuration of the network was sometimes observed. Many prolamellar bodies were also very often observed, which displayed two or three different lattice forms in a single prolamellar body. It became evident from these observations that most, if not all, of the prolamellar bodies in the squash etioplasts are paracrystalline network of spinel-type twin which is composed of two or more domains of zincblende-type. We propose a three dimensional model of the squash prolamellar body in which five paracrystal domains of zincblende-type are assembled around a pentagonal column at the center and connected by boundary lattice layers of wurtzite-type.

Sea urchin paramyosin

Abstract 1. 1. Paramyosin-like protein was extracted and purified from the lantern muscle of sea urchins mostly of Pseudocentrotus depressus . 2. 2. The amino acid composition, the circular dichroism spectrum and the subunit molecular weight of this protein are characteristically similar to those of the known paramyosin, while the sedimentation coefficient was considerably larger. 3. 3. Paracrystals with an axial peridicity of about 154 A were formed by divalent cations but those with 725 A periodicity, which are typically formed in the known paramyosin, were not formed. 4. 4. The sea urchin paramyosin is likely to form cores of thick filaments in the echinoderm.

Inhibition of photophosphorylation by ATP and the role of magnesium in photophosphorylation

ATP and pyrophosphate at high concentration (greater than 1 mM) inhibited photophosphorylation of isolated spinach chloroplasts in the normal salt medium and did not cause stimulation of electron transport. The inhibition of photophosphorylation by ATP or pyrophosphate was shown to be abolished by the addition of excess MgCl2, ADP and phosphate. It has been demonstrated that the rates of photophosphorylation in the absence and presence of ATP or pyrophosphate are determined similarly by the concentrations of magnesium-ADP (Mg - ADP-) and magnesiumphosphate (Mg - Pi) complexes. It is highly probable that Mg - ADP- and Mg - Pi, but not free ADP and free phosphate, are the active form of the substrates of photophosphorylation. This is in support of the view that ATP inhibits photophosphorylation by decreasing the concentration of Mg2+ which is available for the formation of the complex with ADP and phosphate.

An artificial CuII complex with intriguing oxygen radical-quenching profile. X-ray structure, cytochrome c assay, and ESR study.

A novel artificial peptide named HPH-Pep, comprising a pyridine and two histidine units, was synthesized. The HPH-Pep-CuII complex had unique pentacoordinated structure as shown by X-ray crystallography and exhibited superoxide-scavenging activity as indicated by ESR spectroscopy. The superoxide-quenching profile of HPH-Pep-CuII was studied in detail by cytochrome c assay and ESR spin trapping and it was found that (1) HPH-Pep-CuII did not scavenge hydrogen peroxide or hydroxyl radical and hence the scavenging activity was specific to superoxide, and (2) HPH-Pep-CuII did not generate hydrogen peroxide upon scavenging superoxide.

Prolamellar body and saponins: Avenacosides are not constituents of Avena etioplasts.

Etiolated Avena leaf cells were homogenized, then fractionated into four fractions in the presence of salts by differential centrifugation, and intact etioplasts were prepared by Percoll or sucrose density gradient centrifugation. Using thin layer chromatography steroidal saponins, avenacoside A and B were found in the leaf cells and heavy cell fractions which were rich in other cell structures besides intact etioplasts, but not detected in the purified etioplasts. We concluded that saponins are not constituents of the prolamellar bodies in etioplasts.

Characterization of Two forms of Pchld (Pchld 650 and Pchld 640) in Pchld Holochrome Solubilized with Detergents from Squash Etioplast Membranes

The inner membranes of squash etioplast contain two spectral forms of photoactive protochlorophyllide(Pchld), Pchld 650 and Pchld 640; the major and minor component, respectively(Ikeuchi, Murakami 1983). They are believed to be a ternary complex associated with NADPH and Pchld reductase(PR). When the membranes are illuminated by a single flash at 23 C, these two Pchlds are instantaneously converted to a short-lived form of chlorophyllide(Chld) peaking at 678 nm(Chld 678), and then transformed in the dark to another form of Chld peaking at 684 nm(Chld 684). In the membranes frozen below -20 C Chld 678 is not transformed to Chld 684 even after long dark incubation.