Biomedical subjects

H Yamamura

Publications and source records attributed to H Yamamura.

At least 19 recordsLinked to original sources

PubMed1992

Thrombin-induced human platelet aggregation is inhibited by protein-tyrosine kinase inhibitors, ST638 and genistein.

We have investigated the involvement of protein-tyrosine kinases in thrombin-induced aggregation of human platelets, using ST638 and genistein which are known inhibitors of protein-tyrosine kinase. Preincubation of platelets with 50 microM of ST638 or 25 micrograms/ml of genistein completely blocked the platelet aggregation induced with 0.05 unit/ml of thrombin. The increase of protein-tyrosine phosphorylation bands (135-, 124-, 76-, 64-, and 60-kDa) induced with thrombin was also inhibited by these inhibitors in a dose-dependent manner. These inhibitors also blocked the platelet aggregation and protein-tyrosine phosphorylation induced with thrombin in aspirin-treated platelets. Increase of the intracellular Ca2+ concentration induced by thrombin was also inhibited by higher concentrations of genistein. These results suggest that the protein-tyrosine phosphorylation plays a certain role in platelet activation having some relation to the intracellular Ca2+ concentration.

Amino Acid Sequence↗

PubMed1992

Protein-tyrosine kinase p72syk is activated by wheat germ agglutinin in platelets.

We previously reported a molecular cloning of porcine gene syk encoding a non-receptor type 72-kDa protein-tyrosine kinase (Taniguchi et al. (1991) J. Biol. Chem. 266, 15790-15796). In this study, we have demonstrated that p72syk is expressed in porcine platelets at 0.1-0.2% of total protein and that the lectin wheat germ agglutinin induces an activation of p72syk against both auto- and exogenous-substrate-phosphorylation in porcine platelets. The activation of p72syk was abrogated by the coexistence of N-acetyl-D-glucosamine with wheat germ agglutinin. These data suggest that p72syk is a candidate of responsible protein-tyrosine kinase for platelet activation and that cell surface glycoprotein is involved in the activation of p72syk in platelets.

Acetylglucosamine↗

PubMed1992

Protein-tyrosine phosphorylations induced by concanavalin A and N-formyl-methionyl-leucyl-phenylalanine in human neutrophils.

The ability of the lectin concanavalin A (ConA) and N-formyl-methionyl-leucyl-phenylalanine (fMLF) to induce protein-tyrosine phosphorylation in human neutrophils was examined by immunoblot analysis. ConA caused an increase in tyrosine phosphorylation of protein bands with apparent molecular masses of 120, 80, 76, 66 and 40 kDa; on the other hand, fMLF caused an increase in those of only 80-kDa and 40-kDa proteins. These protein-tyrosine phosphorylations were time- and dose-dependent. The tyrosine phosphorylation of 40-kDa protein induced by fMLF was suppressed but that by ConA was not suppressed by pertussis toxin pretreatment. At the same time, pertussis toxin pretreatment also inhibited lysozyme release and aggregation of neutrophils induced by fMLF but did not inhibit those responses induced by ConA. These results suggest that the tyrosine phosphorylation of 40-kDa protein may be involved in a part of neutrophil activation and be regulated via pleiotropic signal transduction pathways. In addition, immunoblot analysis employing antibodies against microtubule-associated protein 2 (MAP2) kinase suggested that this tyrosine-phosphorylated 40-kDa protein might be the MAP2 kinase.

Blood Proteins↗

PubMed1992

A prospective trial of early detection of pancreatic cancer by ultrasonographic examination combined with measurement of serum elastase 1.

The accuracy of ultrasonographic examination combined with measurement of elastase 1 levels for early detection of pancreatic cancer was evaluated prospectively. Abdominal ultrasonographic examination and measurement of serum elastase 1 levels were done within 2 weeks after the initial visit to the clinic in a total of 2098 patients older than 35 years of age with symptoms suggesting pancreatic disease. Those in which one or both of these examinations had abnormal results underwent additional tests such as endoscopic retrograde cholangiopancreatography and computed tomography. Of those with pancreatosonograms with abnormal results with or without abnormally high serum elastase 1 levels, 19 patients eventually were found to have pancreatic cancer. No patients with pancreatic cancer, a normal level of serum elastase 1, and a pancreatosonogram with normal results were found, but follow-up studies revealed one pancreatic cancer in 189 patients after technically unsatisfactory ultrasonographic examination. In 9 (45%) of the 20 cases detected in this study, the pancreatic cancers were resectable, and two (10%) were less than 2.0 cm in longest diameter. These findings indicate that this combined examination is useful for early detection of pancreatic cancer. However, no pancreatic cancer was found in patients with abnormally high serum elastase 1 levels without a pancreatosonogram with abnormal results. Moreover, a combination of ultrasonographic examination and measurement of the elastase 1 level did not raise the diagnostic accuracy over that of ultrasonographic examination alone. These findings indicate that ultrasonographic examination alone is useful in screening for early pancreatic cancer.

Adult↗

PubMed1992

Developmental alteration of serotonin neurons in the raphe nucleus of rats with methylazoxymethanol-induced microcephaly.

Prenatal exposure of pregnant rats to methylazoxymethanol acetate (MAM), an anti-mitotic agent, on day 15 of gestation induces severe microcephaly in the offspring. The present study first investigated a developmental alteration of serotonin (5HT) neurons immunohistochemically in the dorsal and median raphe nuclei in serial sections in both control and microcephalic rats (MAM-rats) at 35 days of age. 5HT-immunoreactive neurons in the MAM-rats were reduced in number and irregularly distributed in the dorsal and median raphe nuclei compared with those in the control. The dendrites of neurons in these nuclei in the MAM-rats were very short and twisted. A follow-up observation on the development of the cerebral cortex at 5, 9 and 28 days of age was performed using Nissl-stained preparations, which revealed a disorganized cell arrangement in the cerebral cortex of the MAM-rats at the very early postnatal period. Furthermore, the distribution of 5HT-immunoreactive fibers into the cerebral cortex was also examined using brains of 28 days of age. In MAM-rats of this age, abnormally tortuous 5HT-immunoreactive fibers were observed in the cerebral cortex. 5HT neurons in the raphe nuclei are known to project their ascending axons widely into the entire cortical area during the 1st postnatal week. Thus, the association of disorganized cortical cell arrangement and the hyperdense and tortuous distribution of 5HT-immunoreactive fibers in the cerebral cortex support the idea of target-dependent secondary degeneration of 5HT neurons in the dorsal and median raphe nuclei of the MAM-rats.

Animals↗

PubMed1992

Phosphorylation of histone H2A by protein kinase C and identification of the phosphorylation site.

In regenerating rat liver, nuclear protein histone H2A was shown to be phosphorylated on its amino-terminal serine residue [Sung et al. (1971) J. Biol. Chem. 246, 1358-1364], but the protein kinase which phosphorylates this residue has not been identified. To evaluate the possibility that protein kinase C can phosphorylate this residue, calf thymus histone H2A was 32P-labeled by incubation with [gamma-32P]ATP and highly purified protein kinase C from rat brain in the presence of calcium and phospholipid. About 1 mol of 32P was incorporated per mol of histone H2A and the Km and apparent Vmax of the reaction were calculated to be 2.1 microM and 0.35 mumol/min/mg, respectively. So histone H2A seemed to be a good substrate for protein kinase C. Further, the proteolytic phosphopeptides of 32P-labeled histone H2A were isolated by means of a series of column chromatographies and analyzed for their amino acid compositions. Comparison of the data with the known primary structure of histone H2A revealed their amino acid sequence as 1Ser-Gly-Arg. These data suggest that protein kinase C may be a candidate for the protein kinase which phosphorylates the amino-terminal serine residue of histone H2A during the regeneration of rat liver.

Amino Acid Sequence↗

PubMed1992

Inhibitory effect of mitoxantrone on activity of protein kinase C and growth of HL60 cells.

Mitoxantrone, a new anthraquinone, showed inhibitory an effect on protein kinase C (PKC) activity. Its IC50 value was 4.4 micrograms/ml (8.5 microM), which is much lower than those of the well-known anthracyclines daunorubicin and doxorubicin, the IC50 values of which are more than 100 micrograms/ml (> 170 microM). Kinetic studies demonstrated that mitoxantrone inhibited PKC in a competitive manner with respect to histone H1, and its Ki value was 6.3 microM (Ki values of daunorubicin and doxorubicin were 0.89 and 0.15 mM, respectively), and in a non-competitive manner with respect to phosphatidylserine and ATP. Inhibition of phosphorylation by mitoxantrone was observed with various substrates including S6 peptide, myelin basic protein and its peptide substrate derived from the amino-terminal region. Their IC50 values were 0.49 microgram/ml (0.95 microM), 1.8 micrograms/ml (3.5 microM), and 0.82 microgram/ml (1.6 microM), respectively. Mitoxantrone did not markedly inhibit the activity of cyclic AMP-dependent protein kinase, casein kinase I or casein kinase II, at concentrations of less than 10 micrograms/ml. On the other hand, brief exposure (5 min) of HL60 cells to mitoxantrone caused the inhibition of cell growth with an IC50 value of 52 ng/ml (0.1 microM). In HL60 cells, most of the PKC activity (about 90%) was detected in the cytosolic fraction. When HL60 cells exposed to 10 micrograms/ml mitoxantrone for 5 min were observed with fluorescence microscopy, the fluorescence elicited from mitoxantrone was detected in the extranuclear area. These results indicated that mitoxantrone is a potent inhibitor of PKC, and this inhibition may be one of the mechanisms of antitumor activity of mitoxantrone.

Animals↗

PubMed1992

Transfer of 125I-albumin from blood to brain in newborn rats and the effect of hyperbilirubinemia on the transfer.

Transfer of albumin from blood into cerebellum and cerebrum was examined in postnatal rats. 125I-Albumin was injected into rats on day 3, 7, 14, 28 or 70. The ratio of albumin concentration in the cerebellum or in the cerebrum to that in the plasma 2 h after the injection, hereinafter termed the relative albumin level (RA), was calculated and used as a criterion for the albumin transfer. The RA in both the cerebellum and the cerebrum decreased with age, but plateaued between days 28 and 70. The level was significantly higher in the cerebellum than in the cerebrum on days 3 and 7. This was not observed, however, on days 28 and 70. Significant correlations were indicated between 125I-albumin levels in the plasma and those in the cerebellum or cerebrum on days 7 and 14, but not on day 28. No significant difference in the RA in the cerebellum and the cerebrum was detected between jaundiced homozygous Gunn rats and control nonjaundiced rats at all ages examined. These results demonstrated that albumin could enter the brain tissue from the blood at least until postnatal day 14 and that the endogenous bilirubin had no effect on the albumin transfer into the brain. The relationship between the immaturity of brain and the transfer of albumin into the brain was discussed.

Age Factors↗

PubMed1992

Transfer of bilirubin covalently bound to 125I-albumin from blood to brain in the Gunn rat newborn.

Transfer of bilirubin covalently bound to albumin (Alb.B) from blood into brain was examined in Gunn rats at postnatal day 3, 7, 14, 28 or 70. The ratio of the 125I-Alb.B concentration in the brain to that in the plasma 2 h after the injection (RAB) was used as a criterion for Alb.B transfer. RAB in brain decreased with age until day 28. Significant correlations were indicated between 125I-Alb.B plasma levels and those in the brain at days 7 and 14, but not at day 28. These results suggested that 125I-Alb.B could transfer from the blood to the brain until day 14. Comparison of the relative amount of radioactivity accumulated in the brain by a 125I-Alb.B injection with that of 125I-albumin alone revealed higher radioactivity in the former than the latter only at day 14, suggesting a transient appearance of particular cellular elements with high affinity to bilirubin in the developmental stage of the brain.

Aging↗

PubMed1992

A tiaramide derivative, 5-chloro-3-(4-hydroxypiperadinocarbonylmethyl)benzothiazoline-2-one (HPR-611), a potent inhibitor of anaphylactic chemical mediator release--a distinctive feature from disodium cromoglycate.

Effects of a tiaramide derivative, 5-chloro-3-(4-hydroxypiperadinocarbonylmethyl)benzothiazoline++ +-2-one (HPR-611), on anaphylactic chemical mediator release from rat peritoneal exudate cells (RPEC), guinea pig lung fragments (GPLF) and human lung fragments (HLF) were investigated in comparison with those of tiaramide and disodium cromoglycate (DSCG). HPR-611 at 10(-6) - 10(-4) g/ml showed a concentration-dependent inhibition of the histamine release from RPEC regardless of its pretreatment time. Tiaramide also inhibited the release with slightly less potency than HPR-611. The treatment of DSCG 1 min before antigen challenge markedly prevented the release but the inhibitory potency was clearly deteriorated by prolongation of the pretreatment time. Tiaramide tended to influence the anaphylactic release of histamine from GPLF with only 20% inhibition of the release at either 10(-5) or 10(-4) g/ml, whereas HPR-611 at 10(-5) and 10(-4) g/ml significantly suppressed the release in a concentration-dependent fashion. DSCG was not effective on that even at higher concentrations. Anaphylactic release of not only histamine but also immunoreactive leukotriene B4 (i-LTB4) and i-LTC4 from HLF was markedly inhibited by 10(-8) - 10(-4) g/ml of HPR-611. Tiaramide inhibited the release to a somewhat less extent than HPR-611, while nominal or no inhibitions by DSCG were found. From these results, it is clearly apparent that anti-allergic actions of HPR-611 are quite different from those of DSCG.

Animals↗

PubMed1992

Effect of AS-35 on agonist-induced contractions and the resting tonus of airway smooth muscles and the in vitro release of chemical mediators from passively sensitized lung fragments from humans and guinea pigs.

Effects of 9-[(4-acetyl-3-hydroxy-2-n-propylphenoxy)methyl]-3-(1H-tetrazol -5-yl)-4H-pyrido[1,2-alpha]pyrimidin-4-one (AS-35) on the resting tonus or contractions induced by agonists, such as leukotriene (LT) D4 and specific antigen of isolated guinea pig tracheas or human bronchi, and the in vitro anaphylactic release of histamine and LTs from human lung fragments were investigated and compared with the effects of FPL 55712 and disodium cromoglycate. AS-35 as well as FPL 55712 did not affect the contractions induced by acetylcholine and histamine of the isolated guinea pig trachea. However, the compound at relatively low concentrations obviously inhibited contractions induced by LTD4, and the antagonistic activity was stronger than that of FPL 55712. Treatment of the isolated human bronchus with AS-35 tended to induce the inhibition of both LTD4- and antigen-induced contractions and the relaxation of the resting tonus in a concentration-dependent manner. The inhibitory potency at 10(-6) g/ml was slightly stronger than that of FPL 55712, but this was not statistically significant. The anaphylactic release of histamine and LTs from the lung fragments appeared to be inhibited by the treatment with AS-35 5 min prior to the antigen challenge. From these results, it is suggested that AS-35 is effective against allergic asthma through antagonism towards peptide-LTs released anaphylactically in addition to inhibition of the chemical mediator release.

Animals↗

PubMed1992

MCI-826 is a potent and selective antagonist of peptide leukotrienes (p-LTs) and has characteristics distinctive from those of FPL 55712.

Antagonistic effects of a newly synthesized compound, (E)-2,2-diethyl-3'-[2-[2-(4-isopropyl)thiazolyl]ethenyl]succinanilic+ ++ acid sodium salt (MCI-826) on the contraction of the isolated guinea pig trachea and human bronchus induced by various agonists including peptide leukotrienes (p-LTs), histamine, acetylcholine (ACh), prostaglandin (PG) D2 and others were investigated and compared with the effects of a p-LT antagonist, FPL 55712, in some experiments. MCI-826 potently antagonized LTD4- and LTE4-induced contractions at extremely low concentrations in the isolated guinea pig trachea with pA2 values of 8.3 and 8.9, respectively, on a molar basis. These values indicated that MCI-826 is over 100 times stronger than FPL 55712. Similarly, MCI-826 at 10(-8) g/ml (2.4 x 10(-8) M) markedly antagonized LTD4-induced contractions of the isolated human bronchus. Although FPL 55712 fairly inhibited the 10(-9) g/ml LTC4-induced contraction of the isolated guinea pig trachea, MCI-826 had little effect on the contraction at high concentrations like 3 x 10(-6) g/ml (7.1 x 10(-6) M). MCI-826 modestly affected the other agonist-induced contractions and the resting tonus of the isolated guinea pig trachea at 10(-6) g/ml (2.4 x 10(-6) M) or higher concentrations, but FPL 55712 caused fair inhibition of some of those contractions and gradually lowered the resting tonus with time. These results indicate that MCI-826 is a highly potent and selective antagonist of LTD4 and LTE4 and can be a useful tool for biological and pharmacological experiments on p-LTs.

Acetylcholine↗

PubMed1992

Significant role of peptide leukotrienes (p-LTs) in the antigen-induced contractions of human and guinea pig lung parenchymas and bronchi or tracheas in vitro.

Chemical mediators responsible for the antigen-induced contractions of isolated, passively sensitized human and guinea pig lung parenchymas and bronchi or tracheas were evaluated by several antagonists and enzyme inhibitors, with emphasis on the effects of the potent and selective peptide leukotriene (p-LT) antagonist MCI-826. All of these preparations showed long-lasting contractions in response to an antigen challenge which lasted for more than 60 min. In either the human lung parenchyma and brochus or guinea pig lung parenchyma, pretreatment with 10(6) g/ml (2.4 x 10)-6) M) MCI-826 significantly inhibited the late phase at 10 to 60 min after the challenge of the contraction following slight suppression of the early phase. The early phase contractions of these preparations were moderately antagonized by 10(-6) g/ml mepyramine, but the late phases were not influenced or even rather enhanced. The combination treatment of MCI-826 with mepyramine additionally and markedly inhibited both phases of these preparations. On the other hand, although mepyramine apparently inhibited the early phase of the guinea pig tracheal contraction but not the late phase, no synergistic inhibitions of the contraction were observed when it was combined with MCI-826. The p-LT antagonist FPL 55712, atropine and indomethacin at 10(-6) g/ml either slightly inhibited or enhanced the contractions of human lung parenchymas, guinea pig tracheas and lung parenchymas, but the effects were not significant. From these results, it should be emphasized that p-LTs largely contribute to induction of the anaphylactic contractions of human lung parenchymas as well as human bronchi and guinea pig lung parenchymas but not guinea pig tracheas.

Animals↗

PubMed1992

Gamma-radiation produces abnormal Bergmann fibers and ectopic granule cells in mouse cerebellar cortex.

Morphological changes in Bergmann glial fibers in the developing cerebellar cortex produced by exposure to gamma-rays were investigated in association with ectopic granule cells. Six-day-old mice that had been exposed to 3 Gy of gamma-radiation were killed 6 hours after exposure or at 7 through 30 days of age. Their cerebella were examined histologically and immunohistochemically for glial fibrillary acidic protein in Bergmann fibers. Extensive cell death took place in the external granular layer (EGL) of the cerebellum from 6 through 24 hours after exposure. This led to the thinning of the EGL and a decrease in the number of migrating cells in the molecular layer. The number of Bergmann cells was not decreased, but the fibers in the molecular layer were distorted; whereas, in the control these fibers were straight and perpendicular to the pial surface. The EGL began to recover 2 days after exposure, and abnormally oriented migrating cells were seen. At 17 days of age, some cell clustering was observed in the molecular layer of the irradiated cerebellum. Distortion of the Bergmann fibers was marked in regions where ectopic granule cells appeared at 30 days of age. These findings suggest that the distortion of Bergmann fibers leads to the production of ectopic granule cells after exposure to gamma-radiation.

Animals↗

PubMed1992

Effect of SA-103 on experimental allergic models in vivo and in vitro--comparison with disodium cromoglycate.

The anti-allergic action of N-[4-(4-methoxyphenyl)-2-thiazolyl]-1H-tetrazol-5-carboxamide (SA-103) was investigated and compared with that of disodium cromoglycate (DSCG). 1) Oral administration of SA-103 (0.1-10 mg/kg, p.o.) showed dose-dependent inhibition of 48 hr homologous passive cutaneous anaphylaxis (PCA) in rats. The inhibition rate (50%) of the compound at 1 mg/kg was comparable to that of DSCG at 1 mg/kg (i.v.). 2) Both of the drugs concentration-dependently inhibited the release of in vitro anaphylactic histamine from rat peritoneal exudate cells, but SA-103 was 1,000 times as potent as DSCG. 3) High doses (50 and 100 mg/kg, p.o.) of SA-103 tended to suppress 7-day homologous PCA in guinea pigs by only 20-30%. DSCG (100 mg/kg, i.v.) did not influence the reaction. 4) Neither anaphylactic histamine nor leukotriene release from guinea pig lung fragments was markedly influenced by SA-103 (10(-8)-10(-5) g/ml) or DSCG (10(-5)-10(-3) g/ml). 5) The histamine and serotonin induced contractions of the isolated guinea pig ileum were minimally enhanced or suppressed by very high concentrations (10(-4) g/ml) of SA-103 and DSCG. In addition to the above results, prolonged treatment with either compound before antigen challenge decreased the inhibitory response to anaphylactic histamine release from rat peritoneal cells. It is suggested, therefore, that the main mechanism(s) of the anti-allergic action of SA-103 is similar to that of DSCG, and SA-103 may be expected to be effective against allergic diseases.

Animals↗

PubMed1992

[The culture of mouse bone marrow-derived mast cells (BMMC) and the anaphylactic release of chemical mediators].

Bone marrow cells from BALB/c, C3H/He and WBB6F1+/+ mice were cultured for 5 wks in the presence of the culture supernatant from prokoweed mitogen-stimulated spleen cells to assess and compare the degree of growth, proliferation and chemical mediator release of the mast cells (BMMC) derived from them. BMMC, which were positive to alcian blue staining, were found in the suspension cells on the culture of the bone marrow cells of either species of mice after 2 wk culture. The percentages of BMMC in the suspension cells were increased with time of culture, reaching more than 90% after 5 wks. No differences in the growth and proliferation rate among BMMC from these three species were observed. However, in regard to the amount of anaphylactic leukotriene (LT) and histamine release. BMMC from BALB/c mice were superior to those from other species. From the above results, subsequent experiments were executed with BMMC from BALB/c mice. There was no obvious difference in the releasability of anaphylactic mediators among BMMC obtained at any stages of the passage during 4-12 wk culture. On the other hand, although BMMC cultured for 4 and 5 wks well responded to Ca ionophore A23187 for these mediator release, those for 6 to 12 wks obviously deteriorated with prolongation of the culture. The time course of the anaphylactic release of immunoreactive (i-) LTB4, i-LTC4 and histamine from BMMC revealed that almost maximum release was reached at 10, 20 and 5 min, respectively, after antigen challenge. Several drugs including antiallergics and beta-stimulants had no effect on their release. From these results, it is suggested that present BMMC may be inadequate cells for evaluation of antiallergic drugs that can inhibit the anaphylactic mediator release, but may be useful for the research of the mechanism of the release because the cells likely release the mediators without occurrence of complicated subordinate reactions.

Animals↗

PubMed1992

Ophthalmotoxicity and ototoxicity of the new quinolone antibacterial agent levofloxacin in Long Evans rats.

An ophthalomo- and ototoxicity study of a new quinolone antibacterial agent, (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1- piperazinyl)-7-oxo-7H-pyrido[1,2,3-de] [1,4]benzoxazine-6-carboxylic acid hemihydrate (levofloxacin, DR-3355, CAS 100986-85-4) was investigated in Long Evans rats. The rats were orally administered 100 mg/kg of DR-3355, ciprofloxacin (CPFX), norfloxacin (NFLX) or nalidixic acid (NA) for 2 weeks, and the effects on visual and auditory functions were examined. Examination of electroretinograms (ERGs) revealed a decrease in the amplitudes of the a- and b-waves, a prolongation of the latency and diminution or disappearance of oscillatory potential waves in NA treated rats. Similar but milder changes were also noted in the NFLX treated rats. ERGs from DR-3355 or CPFX treated rats were normal. Histopathological examination revealed no changes suggestive of ophthalmotoxicity or ototoxicity in the rats treated with DR-3355, CPFX or NFLX. On the other hand, NA treated rats showed partial loss of the outer hair cells of the organ of Corti in the cochlea, suggesting that NA had slight ototoxicity. DR-3355 did not show any deleterious visual or auditory effects at the dose used in this study.

Animals↗

PubMed1991

Identification of the phosphorylation sites of H2B histone by a catalytic fragment of p72syk from porcine spleen.

Phosphorylated sites of calf thymus H2B histone were investigated with a catalytic fragment of 72 kDa protein-tyrosine kinase (p72syk). Three of five tyrosine residues in H2B histone can be phosphorylated by this kinase. In this analysis, H2B histone was thoroughly phosphorylated in vitro with [gamma-32P]ATP and the kinase, and then digested with a lysylendopeptidase. The resulting radioactive phosphopeptides were separated by a reverse-phase column on high performance liquid chromatography. Subsequent sequential Edman degradation of the purified phosphopeptides revealed that 40Y, 83Y and 121Y were phosphorylated. 121Y is the major phosphorylated residue in H2B histone. No phosphorylation was detected in 37Y and 42Y. Although the consensus sequence was not defined from these analyses, our data suggest that higher-order structure(s) in addition to primary one may participate in recognition of H2B histone by this protein kinase.

Amino Acid Sequence↗