Biomedical subjects

T Mizobata

Publications and source records attributed to T Mizobata.

23 records · Page 2Linked to original sources

PubMed1993

Refolding of yeast enolase in the presence of the chaperonin GroE. The nucleotide specificity of GroE and the role of GroES.

GroE, a chaperonin protein from Escherichia coli, facilitates the folding of numerous proteins by binding to protein-folding intermediates and suppressing aggregation (Gething, M., and Sambrook, J. (1992) Nature 355, 33-45). The specific mechanism of GroE-facilitated folding involves numerous interactions between GroEL, GroES, the refolding protein, and ATP. In the present study, we have probed the molecular characteristics of the refolding reaction of yeast enolase in the presence of GroE. We have found that (a) GroEL interacts specifically with enolase during the folding reaction, resulting in folding arrest; (b) the release of partially folded molecules of enolase from the GroE complex may be mediated by the addition of nucleotides other than ATP (ADP, CTP, and UTP); and (c) GroES is required for enolase to be released from GroEL in the presence of ADP, CTP, and UTP but not required in the presence of ATP. The nucleotide binding mechanism of GroEL and the specific role of GroES during the refolding reaction are discussed in detail.

Adenosine Triphosphate↗

PubMed1992

Effects of the chaperonin GroE on the refolding of tryptophanase from Escherichia coli. Refolding is enhanced in the presence of ADP.

The refolding of the tetrameric enzyme tryptophanase was facilitated by the chaperonin GroE. Maximum refolding yield of tryptophanase molecules (about 80%) was attained in the presence of a 15-fold excess of GroE 21-mer over tryptophanase monomer. The GroEL subunit was required for this improvement in refolding yield, whereas the GroES subunit was not. Light scattering experiments of the refolding reaction revealed that GroE bound to tryptophanase folding intermediates and suppressed their aggregation. The presence of ATP was required for the efficient dissociation of tryptophanase from GroEL. However, our experiments indicated that tryptophanase dissociated readily from GroEL in the presence of not only ATP, but also in the presence of non-hydrolyzable ATP analogues such as ATP gamma S (adenosine 5'-O-(3-thiotriphosphate)) and AMP-PNP (adenyl-5'-yl imidodiphosphate) as well. Surprisingly, the release of tryptophanase from GroEL was facilitated in the presence of ADP as well. We concluded that the binding of nucleotides such as ATP and ADP changed the conformation of GroEL and facilitated the dissociation of tryptophanase molecules. The conformation formed in the presence of ADP was distinct from the conformation formed in the presence of ATP, as shown by the selective dissociation of various folding proteins from the two conformations.

Adenine Nucleotides↗

PubMed1992

[Direct injection chemotherapy combined with arterial embolization in the treatment of liver cancers].

Direct injection chemotherapy in combination with transcatheter arterial embolization (TAE) was carried out in primary and secondary liver cancers. In this treatment, the anticancer agents dissolved in contrast media were directly injected into the tumor tissue with the echo-guided puncture needle after TAE. The dynamics of the injected drugs marked with non-ionic and water-soluble contrast media was followed up by the sequential CT studies, on which the contrast media was observed only in the tumor area in 18 out of 30 nodules from 2 to 8 weeks after the injection. The procedure is considered an effective drug delivery system to achieve a targeting chemotherapy in the liver cancers.

Antineoplastic Agents↗

PubMed1990

Role of tryptophan 248 in the active site of tryptophanase from Escherichia coli.

Tryptophan 248, located in the active site of tryptophanase from Escherichia coli, has been replaced with phenylalanine by site-directed mutagenesis. Judging from CD and fluorescence spectra, the global structure of the mutant enzyme was found to be the same as that of the wild-type enzyme. The binding affinity of the mutant enzyme for the coenzyme pyridoxal 5'-phosphate (PLP) was reduced tenfold compared to the wild-type enzyme. Kinetic analyses under PLP-saturated conditions indicated that the Km values of the mutant enzyme for substrates are the same as those of wild-type enzyme but the kcat values are decreased to about 85%, which accounts for the overall activity decrease. These findings suggest that tryptophan 248 interacts closely with PLP and plays an important role in the catalytic reaction.

Animals↗

PubMedDate not supplied

Clear cell sarcoma of the kidney in an adult.

A 25-year-old woman with clear cell sarcoma of the kidney (CCSK) underwent computed tomography (CT), angiography, and a surgical operation. The clear cell sarcoma showed a cystic lesion with solid components on CT and a hypovascular tumor and rat-tail occlusion of the left renal artery on angiography. These findings in our adult case of CCSK corresponded with those of CCSK in childhood.

Adult↗