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Volume 25, Issue 5
Displaying 1-5 of 5 articles from this issue
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Structural Changes of Bacteriorhodopsin Induced by Electric FieldKinko TSUJI1985 Volume 25 Issue 5 Pages 183-191
Published: September 25, 1985
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSElectrooptical methods are very useful for studies on structural and functional changes of membrane-bound proteins, because the membrane potential plays an important role on the structure, and therefore on transport of ions and/or molecules through the membrane. In this review article electrooptical studies of bacteriorhodopsin of halobacterial purple membrane is summarized as an example. Conformational changes of bacteriorhodopsin are induced by electric pulses both in suspensions and in dried films. The absorbance change induced by the electric field of 2-20kV/cm with a duration <100/μs in suspension consists of dichroic and isotropic contributions, which have been suggested to correspond to changes in the orientation of both retinal and tyrosin and/or tryptophane residues and to changes of the microenvironment of aromatic amino acid residues concomitant with pK changes in at least two types of proton binding sites, respectively. The absorbance change due to the external field of-300kV/cm (duration 3-5 minutes) in dried films reveals that the electric field from the intracellular side to the extracellular side of purple species of purple membrane induces an intermediate similar to the cation-depleted blue species. The electric dichroism is also observed in the dried film where the membrane fragments are fixed, suggesting the angular displacement of the retinal transition moment.View full abstractDownload PDF (940K) -
Pressure Dependence of Protease ReactionsShigeru KUNUGI, Mitsuhiro Fukuda1985 Volume 25 Issue 5 Pages 192-202
Published: September 25, 1985
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSHighly specific and effective catalysis exhibited by enzyme is realized through the three dimensional structure of enzyme protein. For its structure many interactions are working. Besides the interprotein (inter-polypeptide) interactions, those between waters (in and on the protein) and the polypeptides are very important. The hydration of enzyme protein has a dynamic character and coupled with the kinetic function of the catalyst.
To understand the importance of the hydration of enzyme protein, the studies on the pressure dependence of enzyme reactions, mainly protease reactions, carried out in the authors' laboratories, are summarized. The studies on the sequential hydration of dried enzyme (lysozyme) and those on the enzyme reactions (lipase) in organic solvent are also briefly reviewed.View full abstractDownload PDF (852K) -
Susumu TERAKAWA1985 Volume 25 Issue 5 Pages 203-212
Published: September 25, 1985
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSEffects of colchicine and chaotropic anions (Cl, Br, I) on membrane excitability were examined in the squid giant axon with a mechanical stress to the axolemma altered by varying the intracellular pressure. When the intracellular pressure was kept at a high level, colchicine and chaotropic anions applied intracellularly suppressed the excitability. However, when the pressure was kept at an ambient level, these reagents did not affect the excitability for long periods of time (>1.5hr). Electron microscopic observations of the internal surface of the axolemma fixed at the high or low pressure revealed that chaotropic anions dissolved almost all cytoskeletal structures covering the membrane in a relatively short time (<0.5 -1hr). These findings indicate that removal of cytoskeletons including microtubules increases the susceptibility of the membrane to mechanical stresses. It is conclusive that microtubules per se can be a mechanical support of the membrane but they are not essentially involved in the molecular mechanism underlying electrical activities of ionic channels.View full abstractDownload PDF (3315K) -
[in Japanese]1985 Volume 25 Issue 5 Pages 213-220
Published: September 25, 1985
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSDownload PDF (714K) -
Walter Stühmer, [in Japanese]1985 Volume 25 Issue 5 Pages 226-228
Published: September 25, 1985
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSDownload PDF (173K)
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