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Biomedical subjects

K Horiuchi

Publications and source records attributed to K Horiuchi.

At least 289 records · Page 16Linked to original sources
PubMed1978

Nucleotide sequence of the recognition site for the restriction-modification enzyme of Escherichia coli B.

The nucleotide sequence of the recognition site for the restriction-modification enzyme of Escherichia coli B (SB site) has been determined. The recognition site is a 15-nucleotide sequence consisting of the trimer 5'TGA3', followed by an 8-nucleotide domain of variable sequence, which in turn is followed by tetramer 5'TGCT3'. The sequence has no 2-fold rotational symmetry. Single base changes in the constant nucleotide domains result in the loss of sensitivity to both restriction and modification. Our data are also consistent with modification occurring by methylation of two adenine residues per SB site: one on the adenine of the trimer 5'TGA3' and the other on the complementary strand on the adenine complementary to the first thymine of the tetramer 5'TGCT3'. All nine independently isolated spontaneous mutants at the SB1 site of bacteriophage f1 are caused by a G-to-T transversion. Mutations at the SB2 site are caused by various single base changes.

Adenine↗
PubMed1978

(Lysyl-Glycyl-Glycyl)5 and (Lysyl-Glycyl-Glycyl)10 as models of histone. Interaction with DNA and acetylation by calf thymus enzyme.

Sequential polypeptides (Lys-Gly-Gly)5 and (Lys-Gly-Gly)10 were synthesized as models for the N-terminal region of H4 histone and their interactions with DNA were studied. The ability of (Lys-Gly-Gly)10 to precipitate DNA was found to be much higher than that of (Lys-Gly-Gly)5. For example, at the physiological salt concentration, (Lys-Gly-Gly)10 precipitates DNA but (Lys-Gly-Gly)5 does not. Both peptides could be acetylated by a partially purified histone acetyltransferase preparation derived from calf thymus. epsilon-Amino groups of lysyl residues were the sites of the acetylation. DNA-cellulose chromatography of the products indicated that acetylation weakened the interaction of the peptides with DNA.

Acetylation↗
PubMed1978

Enzymic acetylation of nucleosome histone.

Rat liver chromatin prepared from purified nuclei catalyzed the acetylation of histones in nucleosomes at the same level as that of nuclei. The activity of histone acetyltransferase in chromatin was destroyed by heat treatment at 65 degrees C for 5 min. Histones in exogenously added nucleosomes also served as substrate for the enzyme. The sites of acetylation in the nucleosomes appeared to be in the trypsin-digestable N-terminal regions of histones H4, H3, and H2A, as has been reported in an in vivo system.

Acetyl Coenzyme A↗
PubMed1977

Nucleotide sequences near the origin of replication of bacteriophage f1.

The nucleotide sequence of a region related to the initiation of the reaction in which single-stranded DNA gives rise to the replicative form (complementary strand synthesis) in bacteriophage f1 has been determined. The sequence can be drawn in an extensively base-paired structure, i.e., a single hairpin-helix 55 bases long.

Bacteriophages↗
PubMed1977

Effect of high-pass filter on auditory brain stem responses to tone pips.

The effect of high-pass filters on the vertex-positive brain stem response to tone pips at 500, 1000, 2000 and 4000 Hz was investigated in normal adults. The tape-recorded responses were averaged through high pass filters with 3 dB attenuation at 50, 100 and 200 Hz and with a slope of 6 dB/oct, and their amplitudes were compared with those of the averaged responses without filtering. These 3 filters reduced the amplitudes of the responses to 500-Hz tone pips by 3.3, 7.1 and 10.6 dB respectively. On the other hand, the mean attenuations caused by the same series of filters on the response amplitudes at 2000 Hz were only 0.2, 2.9 and 5.4 dB respectively. The responses at 4000 Hz were similar to those at 2000 Hz. This distinct difference in the effect of the high-pass filters suggests that the dominant frequency component of the brain stem response at 500 Hz is significantly lower than that at 2000 Hz and above. The results indicate that the use of a high-pass filter with cutoff frequency over 50 Hz is not recommended for recording the slow positive deflection of the brain stem response to low frequency tones.

Auditory Pathways↗