Functional relationships between cyclodextrin glucanotransferase from an alkalophilic Bacillus and α-amylases Site-directed mutagenesis of the conserved two Asp and one Glu residues

AbstractComparison of the amino acid sequences of cyclodextrin glucanotransferases (CGTases) with those of α-amylases revealed that two Asp and one Glu residues, which are considered to be the catalytic residues in α-amylases, were also conserved in CGTases. To analyze the function of the three conserved amino acid residues in CGTases, site-directed mutagenesis was carried out. The three mutant CGTases, in which Asp229, Glu257 and Asp328 were individually replaced by Asn or Gln, completely lost both their starch-degrading and β-cyclodextrin-forming activities, whereas another mutant CGTase, in which Glu264 replaced by Gln, retained these activities. The three inactive enzymes retained the ability to be bound to starch. These results suggest that Asp229, Glu257 and Asp328 play an important role in the enzymatic reaction catalyzed by CGTase and that a similar catalytic mechanism is present in both CGTases and α-amylases

An oxyl/oxo mechanism for dioxygen bond formation in PSII revealed by X-ray free electron lasers

Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II (PSII) with linear progression through five S-state intermediates (S0 to S4). To reveal the mechanism of water oxidation, we analyzed structures of PSII in the S1, S2, and S3 states by x-ray free-electron laser serial crystallography. No insertion of water was found in S2, but flipping of D1 Glu189 upon transition to S3 leads to the opening of a water channel and provides a space for incorporation of an additional oxygen ligand, resulting in an open cubane Mn4CaO6 cluster with an oxyl/oxo bridge. Structural changes of PSII between the different S states reveal cooperative action of substrate water access, proton release, and dioxygen formation in photosynthetic water oxidation

Observation of the acceleration of a single bunch by using the induction device in the kek proton synchrotron

A single rf bunch in the KEK proton synchrotron was accelerated with an induction acceleration method from the injection energy of 500 MeV to 5 GeV.</p

コソウキン ニオケル ブンピ タンパクシツ ト マク タンパクシツ ノ シキベツ ト キョクザイカ ノ ネットワーク

研究課題番号: 1246003

Comparison of the Peptide Composition of Two Histocompatibility-2 Alloantigens

The peptide composition of purified Histocompatibility-2 (H-2) reactive glycoprotein fragments from two murine strains allelic at the H-2 locus (H-2(b) and H-2(d)) were compared by a cellulose thin-layer peptide mapping micro technique. Approximately 70 per cent of the theoretical maximum number of peptides produced by cyanogen bromide cleavage and trypsin digestion were visualized by this technique. Most (38) of the peptides for the glycoproteins from these strains allelic for the H-2 locus were identical; however, three peptides of the H-2(b) and four peptides of the H-2(d) alloantigen were unique. The results demonstrate the remarkable similarity in protein structure between these two allelic products, but also show a small but reproducible difference in their peptide composition. The findings are consistent with the hypothesis that protein primary structure may determine wholly or in part their alloantigenic activities