Biomedical subjects

Toru Hisabori

Publications and source records attributed to Toru Hisabori.

22 records · Page 2Linked to original sources

PubMed2002

Molecular devices of chloroplast F(1)-ATP synthase for the regulation.

In chloroplasts, synthesis of ATP is energetically coupled with the utilization of a proton gradient formed by photosynthetic electron transport. The involved enzyme, the chloroplast ATP synthase, can potentially hydrolyze ATP when the magnitude of the transmembrane electrochemical potential difference of protons (Delta(micro)H(+)) is small, e.g. at low light intensity or in the dark. To prevent this wasteful consumption of ATP, the activity of chloroplast ATP synthase is regulated as the occasion may demand. As regulation systems Delta(micro)H(+) activation, thiol modulation, tight binding of ADP and the role of the intrinsic inhibitory subunit epsilon is well documented. In this article, we discuss recent progress in understanding of the regulation system of the chloroplast ATP synthase at the molecular level.

Adenosine Triphosphate↗

PubMed2002

Substitution of a single amino acid switches the tentoxin-resistant thermophilic F1-ATPase into a tentoxin-sensitive enzyme.

In contrast to the homologous bacterial and mitochondrial enzymes the chloroplast F(1)-ATPase (CF(1)) is strongly affected by the phytopathogenic inhibitor tentoxin. Based on structural information obtained from crystals of a CF(1)-tentoxin co-complex (Groth, G. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 3464-3468) we have replaced residues betaSer(66) and alphaArg(132) in the alpha(3)beta(3)gamma subcomplex of the thermophilic F(1)-ATPase from Bacillus PS3 by the corresponding residues of the chloroplast ATPase to confer tentoxin sensitivity to the thermophilic enzyme. The mutation alphaArg(132) --> Pro, proposed to relieve steric constraints on tentoxin binding, did not have any significant effect. However, mutation betaSer(66) --> Ala, predicted to provide a crucial hydrogen bond with the inhibitor, resulted in tentoxin inhibition of ATP hydrolysis comparable with the situation found with the chloroplast enzyme.

Adenosine Triphosphate↗

PubMed2002

A facilitated electron transfer of copper--zinc superoxide dismutase (SOD) based on a cysteine-bridged SOD electrode.

The direct electrochemical redox reaction of bovine erythrocyte copper--zinc superoxide dismutase (Cu(2)Zn(2)SOD) was clearly observed at a gold electrode modified with a self-assembled monolayer (SAM) of cysteine in phosphate buffer solution containing SOD, although its reaction could not be observed at the bare electrode. In this case, SOD was found to be stably confined on the SAM of cysteine and the redox response could be observed even when the cysteine-SAM electrode used in the SOD solution was transferred to the pure electrolyte solution containing no SOD, suggesting the permanent binding of SOD via the SAM of cysteine on the electrode surface. The electrode reaction of the SOD confined on the cysteine-SAM electrode was found to be quasi-reversible with the formal potential of 65 +/- 3 mV vs. Ag/AgCl and its kinetic parameters were estimated: the electron transfer rate constant k(s) is 1.2 +/- 0.2 s(-1) and the anodic (alpha(a)) and cathodic (alpha(c)) transfer coefficients are 0.39 +/- 0.02 and 0.61 +/- 0.02, respectively. The assignment of the redox peak of SOD at the cysteine-SAM modified electrode could be sufficiently carried out using the native SOD (Cu(2)Zn(2)SOD), its Cu- or Zn-free derivatives (E(2)Zn(2)SOD and Cu(2)E(2)SOD, E designates an empty site) and the SOD reconstituted from E(2)Zn(2)SOD and Cu(2+). The Cu complex moiety, the active site for the enzymatic dismutation of the superoxide ion, was characterized to be also the electroactive site of SOD. In addition, we found that the SOD confined on the electrode can be expected to possess its inherent enzymatic activity for dismutation of the superoxide ion.

Aminobutyrates↗

PubMedDate not supplied

Towards a functional dissection of thioredoxin networks in plant cells.

Thioredoxins are a ubiquitous family of redox equivalent mediators, long considered to possess a limited number of target enzymes. Recent progress in proteomic research has allowed the identification of a wide variety of candidate proteins with which this small protein may interact in vivo. Moreover, the activity of thioredoxin itself has been recently found to be subject to regulation by posttranslational modifications, adding an additional level of complexity to the function of this intriguing enzyme family. The current review charts the technical progress made in the continuing discovery of the numerous and diverse roles played by these proteins in the regulation of redox networks in plant cells.

Amino Acid Sequence↗