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Biomedical subjects

H Yamagata

Publications and source records attributed to H Yamagata.

At least 19 recordsLinked to original sources
PubMed1995

Cloning, subcellular localization and expression of CHL1, a subunit of magnesium-chelatase in soybean.

Mg-insertion is the first committed step in chlorophyll synthesis and is catalyzed by Mg-chelatase. In photosynthetic bacteria, bchI gene product was suggested to be a subunit of Mg-chelatase. We isolated a bchI homolog from a soybean cDNA library and designated it as chlI. CHLI consisted of 421 amino acid residues and the sequence exhibited a high similarity to other BchI homologs. CHLI contained an ATP-binding motif found in other BchI homologs. CHLI was localized in the soluble fraction in soybean chloroplasts, suggesting that it was a stromal subunit of Mg-chelatase. chlI mRNA in cell culture (SB-P) of soybean was reversibly induced by light.

Adenosine Triphosphate↗
PubMed1995

Congenital myotonic dystrophy: molecular diagnosis and clinical study.

Recently, an unstable DNA fragment specific to myotonic dystrophy (MyD) was discovered. In affected individuals, a DNA fragment is found that is larger than in normal siblings. Our objectives were to show whether the results of DNA analysis agree with the disease severity and prognosis in congenital myotonic dystrophy (CMyD) by DNA analysis. We investigated three pregnancies (two studied retrospectively) in three families. We genotyped the family members with the Southern blots and the polymerase chain reaction (PCR) analysis. In one case a prenatal diagnosis was carried out using chorionic villus sampling. This report also presents the three cases of affected mothers and CMyD babies with their growth courses. We clarify four main problems in CMyD, namely, respiratory distress, delayed motor development, feeding difficulty, and delayed mental development. The allele size in the range of 10 to 13 kb tended to be present as the adult form of MyD, and 14 to 15 kb as the CMyD. The three CMyD cases whose alleles size in the range of 14 to 15 kb showed various forms of disease and prognosis. We reached the following conclusions: the disease severity and prognosis in babies with CMyD did not correlate with the result of DNA analysis. The DNA analysis is a useful test for prenatal diagnosis. However, it is impossible to predict the disease severity and prognosis in babies with CMyD.

Adult↗
PubMed1992

[A case of Hashimoto's thyroiditis associated with renal tubular acidosis, Sjögren syndrome and empty sella syndrome].

This report describes a 48-year old female patient with Hashimoto's thyroiditis, distal-type renal tubular acidosis (d-RTA), Sjögren syndrome (SjS), and empty sella syndrome (ESS). She has been receiving replacement of thyroxine for Hashimoto's thyroiditis since 1967. She felt muscle weakness and numbness in the extremities and was found to have low serum potassium (2.9 mEq/l) in 1987. Since then she has been administrated potassium chloride orally. She was admitted to our hospital because of recurrence of muscle weakness and numbness of the extremities in November 1990. Laboratory examination revealed that her serum levels of antimicrosomal antibody and anti-thyroglobulin antibody were highly positive (MCHA: x 2(10) x 100, and TGHA: x 100). Furthermore, she was revealed to have 1) d-RTA by oral tolerance tests with the administration of NH4Cl and NaHCO3, 2) SjS by Schirmer test and sialography, and 3) ESS by computed tomography and magnetic resonance imaging examinations of the pituitary. Association of Hashimoto's thyroiditis, d-RTA, SjS and ESS in this case may possibly be caused by common autoimmune mechanism.

Acidosis, Renal Tubular↗
PubMed1992

Efficient production of thermostable Thermus thermophilus xylose isomerase in Escherichia coli and Bacillus brevis.

The xylose (glucose) isomerase from the thermophile Thermus thermophilus seems to have potential for the development of new isomerization processes using high temperatures and slightly acidic pH. The isomerase has an optimum temperature at 95 degrees C, and is also very stable at high temperatures. The optimum pH is around 7.0, close to where by-product formation is minimal. Since Thermus produces only a little of this useful isomerase, the production of the cloned gene in Escherichia coli and Bacillus brevis were compared. Especially B. brevis was able to produce the isomerase efficiently, more than 1 g/l, in spite of the high G + C content (67%) of the Thermus gene, and the presence of codons not frequently used in E. coli or B. brevis.

Aldose-Ketose Isomerases↗
PubMed1992

Reconstitution of the active form from the amino- and carboxyl-terminal fragments of a reactive site-modified subtilisin inhibitor of adzuki beans (Vigna angularis).

The complex of an adzuki bean subtilisin inhibitor (ASI-II) with its target enzyme, prepared at pH 7.6, was subjected to reversed-phase HPLC in a trifluoroacetic acid-acetonitrile system. Two peptide fragments derived from the reactive site-modified ASI-II were obtained. The analyses of the amino acid composition and sequence of these two fragments revealed that one corresponded to the region from the amino-terminal Lys to the reactive site P1 Ala and the other, to the region from the reactive site P1' Asp to the carboxyl-terminal Gly of the inhibitor. Although neither fragment alone showed inhibitory activity against subtilisin, an equimolar mixture of both fragments was found to inhibit strongly the target enzyme, as did the intact inhibitor. Thus, it was suggested that the two fragments have strong specific affinity with each other, regenerating the reactive site-modified ASI-II, to inhibit the target enzyme.

Amino Acids↗
PubMed1992

Mass production of sphingomyelinase of Bacillus cereus by a protein-hyperproducing strain, Bacillus brevis 47, and its purification.

Sphingomyelinase (sphingomyelin cholinephosphohydrolase) [EC 3.1.4.12] of Bacillus cereus was overproduced in a protein-hyperproducing strain, B. brevis 47, by cloning the gene into an expression vector pNU211, which has been developed to express a foreign gene utilizing a promoter and a signal sequence of an outer cell wall protein gene. From 1 liter of culture, about 10 mg of protein was purified to near-homogeneity by two steps of column chromatography; this is almost 500 times higher production compared to the conventional preparation from the original strain, B. cereus IAM 1208. The N-terminal amino acid sequence of the secreted enzyme was identical to that of the authentic enzyme, indicating that the signal sequence for secretion of B. cereus was processed properly in B. brevis 47.

Amino Acid Sequence↗
PubMed1992

Characterization of an extracellular protease inhibitor of Bacillus brevis HPD31 and nucleotide sequence of the corresponding gene.

A novel proteinaceous protease inhibitor was isolated from the culture supernatant of Bacillus brevis HPD31. The protease inhibitor of B. brevis (designated BbrPI) was produced extracellularly in multiple forms having at least three different molecular weights. One of them, BbrPI-a, was purified to near homogeneity and only showed inhibitory activity toward serine proteases, such as trypsin, chymotrypsin, and subtilisin. BbrPI was presumed to form a trypsin-inhibitor complex in a molar ratio of 1:1. The inhibitor was found to be heat resistant at neutral and acidic pHs. The gene coding for BbrPI was cloned into Escherichia coli, and its nucleotide sequence was determined. The sequence suggested that BbrPI is produced with a signal peptide of 24 amino acid residues. The amino acid sequence of the protein deduced from the DNA sequence contained the amino acid sequences of amino termini of the inhibitors, a, b, and c, and their putative precursor determined chemically. The molecular weight of the precursor was about 33,000, and the molecular weights of inhibitors a, b, and c were about 22,000, 23,500, and 24,000, respectively. It is presumed that the secreted precursor protein, which is probably inactive, is cleaved by protease into several active protease inhibitor molecules. BbrPI shows no significant homology to the protease inhibitors described previously and is unique in not having any cysteine residues in its molecule.

Amino Acid Sequence↗
PubMed1992

Cloning, characterization, and inactivation of the Bacillus brevis lon gene.

A gene of Bacillus brevis HPD31 analogous to the Escherichia coli lon gene has been cloned and characterized. The cloned gene (B. brevis lon gene) encodes a polypeptide of 779 amino acids with a molecular weight of 87,400 which resembles E. coli protease La, the lon gene product. Fifty-two percent of the amino acid residues of the two polypeptides were identical. The ATP-binding sequences found in E. coli protease La were highly conserved. The promoter of the B. brevis lon gene resembled that recognized by the major RNA polymerase of Bacillus subtilis and did not contain sequences homologous to the E. coli heat shock promoters. The B. brevis lon gene was inactivated by insertion of the neomycin resistance gene. A mutant B. brevis carrying the inactivated lon gene showed diminished ability for the degradation of abnormal polypeptides synthesized in the presence of puromycin.

ATP-Dependent Proteases↗
PubMed1992

Comparison of the myotonic dystrophy associated CTG repeat in European and Japanese populations.

Gene amplification using polymerase chain reaction (PCR) was carried out on DNA samples from a total of 92 normal subjects and 52 subjects with myotonic dystrophy (DM) from European and Japanese populations, to determine the copy number of the CTG repeat associated with DM for each group. In the two populations, the number of repeats on normal chromosomes only were compared, as CTG copy number on DM chromosomes was difficult to determine by PCR alone. In this study, normal chromosomes were found which had as many as 35 copies of the repeat, which is larger than the normal range reported previously but still does not overlap with the repeat number associated with DM pathology, which is at least 50 copies. Using data from normal chromosomes from unrelated subjects, the frequencies of five, 11, and 13 copies of the CTG repeat were found to be significantly different between the two populations, with five and 11 copies more commonly seen in the European population and 13 copies in the Japanese population. This difference may be the result of natural divergence of the normal chromosomes between the population groups.

Alleles↗
PubMed1991

Concentration-related effects of extracellular application of ATP on the action potential and membrane currents of the guinea-pig vas deferens.

The ionic mechanisms underlying concentration-related alterations in the action potential configuration caused by ATP were studied using preparations of the guinea-pig vas deferens voltage-clamped by a double sucrose gap method. Under current-clamp conditions, ATP at concentration of 1.6 microM enhanced the rates of rise and of repolarisation of the action potential whereas at concentration of 1.6 mM it reduced both rates. Under voltage-clamp conditions, lower concentrations increased the maximum inward Ca current without altering kinetics or reversal potential. Higher concentrations reduced the maximum inward Ca current with slowing of rates of activations and inactivation, but also caused a negative shift in reversal potential without affecting conductance. These results suggest that a low ATP concentration activates the voltage-dependent Ca current channels and that the action of a high ATP concentration is related to the internal Ca ion concentration.

Action Potentials↗
PubMed1991

Xylose (glucose) isomerase gene from the thermophile Thermus thermophilus: cloning, sequencing, and comparison with other thermostable xylose isomerases.

The xylose isomerase gene from the thermophile Thermus thermophilus was cloned by using a fragment of the Streptomyces griseofuscus gene as a probe. The complete nucleotide sequence of the gene was determined. T. thermophilus is the most thermophilic organism from which a xylose isomerase gene has been cloned and characterized. The gene codes for a polypeptide of 387 amino acids with a molecular weight of 44,000. The Thermus xylose isomerase is considerably more thermostable than other described xylose isomerases. Production of the enzyme in Escherichia coli, by using the tac promoter, increases the xylose isomerase yield 45-fold compared with production in T. thermophilus. Moreover, the enzyme from E. coli can be purified 20-fold by simply heating the cell extract at 85 degrees C for 10 min. The characteristics of the enzyme made in E. coli are the same as those of enzyme made in T. thermophilus. Comparison of the Thermus xylose isomerase amino acid sequence with xylose isomerase sequences from other organisms showed that amino acids involved in substrate binding and isomerization are well conserved. Analysis of amino acid substitutions that distinguish the Thermus xylose isomerase from other thermostable xylose isomerases suggests that the further increase in thermostability in T. thermophilus is due to substitution of amino acids which react during irreversible inactivation and results also from increased hydrophobicity.

Aldose-Ketose Isomerases↗