Seibutsu Butsuri

Structure and function of Ca2+-ATPase of sarcoplasmic reticulum

Koji Yonekura, Chikashi Toyoshima

1997 Volume 37 Issue 1 Pages 310-314
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.310

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Sarcoplasmic reticulum Ca²⁺-ATPase is an integral membrane protein of Mr 110k and pumps Ca²⁺ against a large concentration gradient during relaxation of muscle. It is a member of Ptype ion pumps that include Na+, K⁺-ATPase and H+, K⁺-ATPase. Elaborated predictions of the secondary structure, assuming 10 transmembrane helices, have been proposed and a large body of experimental evidence seems to support this model. In particular, critical amino-acid residues implicated in the active transport have been identified by site-directed mutagenesis. Its unique three-dimensional structure has been revealed by cryo-electron microscopy. We now have some real structural basis to discuss about the active transport by P-type ion pumps.

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Unusual functions of vanadocytes involved in the accumulation of vanadium in the ascidians

Hitoshi Michibata

1997 Volume 37 Issue 1 Pages 315-320
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.315

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High levels of vanadium corresponding 10⁷ tirnes higher than that in seawater are accumulated in the blood cells of ascidians. Among the about ten types of blood cells, the signet ring cells were revealed to be the true vanadocytes. Vanadium in the vanadocytes was reduced to the +3 oxidation state under pH2. The vanadocytes contained the highest level of sulfate and had H⁺-ATPases in their vacuoles. These findings suggest the possibility that protons, concentrated by H⁺-ATPases, might be linked energetically to the accumulation of vanadium

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Structural Basis for the Molecular Evolution of Glutamyl-tRNA Synthetase

Osamu NUREKI, Shigeyuki YOKOYAMA

1997 Volume 37 Issue 1 Pages 321-325
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.321

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Aminoacyl-tRNA synthetases (aaRS's) play key roles in the correct protein biosynthesis through strict recognition/ligation of the cognate amino acid and tRNA. Our recent study on the crystal structure of glutamyl-tRNA synthetase (GluRS) revealed that GluRS and glutaminyl-tRNA synthetase (GlnRS) share geometrically similar NH2-terminal half, comprising the class I-specific Rossmann-fold domain and the intervening subclass-specific α/β domain. In striking contrast to the β-barrel structure of the GlnRS COOH-terminal half, the GluRS COOH-terminal half displays an all-α-helix architecture, an "α-helix cage". Precise alignment of primary structures of GluRSs and GlnRSs on the basis of the tertiary structures indicates that the gene of GlnRS diverged from that of GluRS in eukaryote, and was transferred laterally from eukaryote to prokaryote ("horizontal gene transfer") in the evolutionary process.

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Hydration characteristics of carbohydrates and physiological functions of trehalose

Minoru SAKURAI, Yoshio INOUE

1997 Volume 37 Issue 1 Pages 326-330
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.326

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First, two representative models to rationalize hydration characteristics of carbohydrates are briefly reviewed. One is a model focusing on the ratio of axial versus equatorial hydroxyl groups. The other is based on the compatibility with water structure depending on the position of the next nearest neighbor hydroxyl groups of a carbohydrate molecule. Next, the hydration property of trehalose is compared with those of maltose and sucrose. Consequently, it is concluded that trehalose is a strong water-structure maker and this property is responsible for its function as a stress protectant of biological materials.

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Swinging lever arm model for force proudction by myosin: Testing by site-directed mutant approach and analyses of the mechanism by structural genetics

Taro Q.P. Uyeda, R. Bruce Patterson

1997 Volume 37 Issue 1 Pages 331-335
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.331

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Myosin is a molecular motor that drives movement of actin filaments. It was recently established that the myosin head undergoes a major shape change during the ATP hydrolysis cycle, leading to the popular hypothesis that the shape change provides motile force. Cellular slime mold is uniquely useful not only as an expression system of site-directed mutant myosins, but also as a genetic system to isolate specific mutant myosin genes and their suppressors out of a population of randomly mutagenized cells. Here we present the power of both sitedirected and random approaches to investigate the significance and mechanism of the conformational changes.

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Nested deletion method using the bacteriophage T3 in vitro packaging system

Yutaka KAWARABAYASI, Hisao FUJISAWA

1997 Volume 37 Issue 1 Pages 336-339
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.336

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[title in Japanese]

[in Japanese], [in Japanese]

1997 Volume 37 Issue 1 Pages 340-341
Published: January 25, 1997
Released on J-STAGE: July 09, 2009

DOIhttps://doi.org/10.2142/biophys.37.340

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