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H Sohma

Publications and source records attributed to H Sohma.

51 records · Page 3Linked to original sources
PubMed1992

Actin binding to cross-linked 10 S smooth muscle myosin and 9 S heavy meromyosin.

Unphosphorylated gizzard myosin and heavy meromyosin were cross linked in the 10 S and 9 S states, respectively, by the cleavable cross linker, 3,3'-dithiobis (sulfosuccinimidyl-propionate) (DTSSP). The 10 S to 6 S transition for cross-linked 10 S myosin appeared to cease; myosin appeared to remain in the 10 S state from measurements of viscosity and Mg(2+)-ATPase activity. The loss of the transition for cross-linked 9 S heavy meromyosin (HMM) was also indicated by Mg(2+)-ATPase activity. The cross links were cleaved by incubation with 50 mM dithiothreitol. From direct binding measurements, the estimated Kd's of actin to cross-linked and control heavy meromyosin were 167 and 16 microM, respectively. The binding affinity of cross-linked HMM to actin was restored to the control level by dithiothreitol.

Actins↗
PubMed1990

Ca2(+)-dependent protein phosphatase which dephosphorylates regulatory light chain-a in scallop smooth muscle myosin.

Ca2(+)-dependent protein phosphatase was purified from scallop adductor smooth muscle by a combination of DEAE-Toyoperal 650S ion exchange chromatographies and gel filtration on Sephacryl S-300. The phosphatase consisted of two subunits having molecular weights of 60 and 19 kDa. Phosphorylated regulatory light chain-a (RLC-a) was dephosphorylated by this phosphatase both in free and bound states in myosin prepared from the opaque portion of scallop smooth muscle (opaque myosin). The dephosphorylation was activated by Ca2+. The half maximal activation was a 1 microM free Ca2+ in the presence of calmodulin and 7 microM free Ca2+ in the absence of calmodulin. Opaque myosin phosphorylated at the heavy chain was not dephosphorylated with this phosphatase. p-Nitrophenyl phosphate was dephosphorylated. In addition to Ca2+, the phosphatase activity for RLC-a was activated by Mn2+, while p-nitrophenylphosphatase activity was activated by Mg2+ more strongly than by Mn2+. The pH-activity curves showed a maximum at pH 7 in the presence of Mn2+, but at around pH 8 in the presence of Mg2+. This phosphatase is similar to phosphatase 2B or calcineurin. The possible regulatory function of this phosphatase in scallop catch muscle is discussed.

Animals↗
PubMed1990

Histone H1 kinase specific to the SPKK motif.

A protein kinase phosphorylating sea urchin spermatogenous histones, H1 and H2B, was found in sea urchin egg homogenate and purified. The kinase is activated by cAMP and is composed of two different types of subunits with molecular masses 41 and 46 kDa. The kinase phosphorylates a peptide, Ser-Pro-Arg-Lys-Ser-Pro-Arg-Lys, which is a double repeat of the DNA-binding SPKK motif [Suzuki M., (1989) EMBO J. 8, 797-804]. We name this kinase SPkinase because it exclusively phosphorylates H1 and H2B, the only histones containing SPKK motifs. Phosphorylation of H1 by SPkinase decreases the DNA-binding ability of H1. This paper is the first to report purification of a kinase which affects the DNA-binding ability of a gene regulatory protein.

Amino Acid Sequence↗
PubMed1988

A cAMP-dependent regulatory protein for RLC-a myosin kinase catalyzing the phosphorylation of scallop smooth muscle myosin light chain.

A cAMP-dependent regulatory protein which modulates the phosphorylation of scallop myosin regulatory light chain-a (RLC-a) by RLC-a myosin kinase (aMK) (Sohma, H. & Morita, F. (1986) J. Biochem. 100, 1155-1163) was purified from the scallop smooth muscle. RLC-a is abundant in the opaque portion of scallop smooth muscle, one of the catch muscles. The regulatory protein for aMK was purified by employing successively DEAE Toyopearl ion exchange chromatography, Sepharose 4B-8(6-aminohexylamino)cAMP affinity chromatography, and Sephadex G 100 gel filtration. The molecular mass of the regulatory protein was 41 kDa, based on the mobility in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. With increasing amounts of the regulatory protein, the aMK activity decreased, and complete inhibition was observed at the concentration of twice that of aMK. The aMK activity inhibited by the regulatory protein was restored by the addition of cAMP. These results suggest that aMK is similar to a catalytic subunit of cAMP-dependent protein kinase, and the protein reported here is similar to its regulatory subunit. aMK may exist as an inactive form, as a combination with this regulatory protein, in vivo and be deinhibited by an increase in the intracellular concentration of cAMP. We discuss a possible correlation between the phosphorylation of RLC-a in myosin catalyzed by aMK and the catch state of the opaque portion of scallop smooth muscle.

Animals↗
PubMed1988

The steady state intermediate of scallop smooth muscle myosin ATPase and effect of light chain phosphorylation. A molecular mechanism for catch contraction.

The ATP-induced difference UV-absorption spectrum of myosin isolated from the opaque portion of scallop smooth muscle (opaque myosin) was Ca2+-sensitive at 40 mM KCl and 1.5 M sucrose. On adding sucrose to 1.5 M, the turbidity of myosin decreased to 24% and the characteristic two forms of the difference spectrum, the ATP-form and ADP-form (Morita, F. (1967) J. Biol. Chem. 242, 4501-4506), were distinguishable. In the presence of Ca2+, the difference spectrum was the ATP-form first and then decayed into the ADP-form with the depletion of ATP. In the absence of Ca2+, however, only the ADP-form was observed. The ADP-form observed in the absence of Ca2+ returned to the ATP-form when the regulatory light chain-a (RLC-a), one of the regulatory light chains of opaque myosin, was phosphorylated. These results suggest that the main intermediate at the steady state of opaque myosin ATPase is converted depending on the concentration of Ca2+, from EPADP in the presence of Ca2+ to EADP in the absence of Ca2+. It changes to EPADP in the absence of Ca2+ on the phosphorylation of RLC-a. Consistent results were obtained by measuring the ATP-induced Trp-fluorescence increase of opaque myosin in the absence of sucrose. Since the opaque portion of scallop smooth muscle is known to be responsible for catch contraction (Ruegg, J.C. (1961) Proc. R. Soc. London Ser. B 154, 224-249), these findings lead us to suppose that the opaque myosin in vivo may stay in the E.ADP complex during the catch state. It changes to EPADP by the phosphorylation of RLC-a, which may terminate the catch state.

Animals↗
PubMed1988

Regulatory light chain-a myosin kinase (aMK) catalyzes phosphorylation of smooth muscle myosin heavy chains of scallop, Patinopecten yessoensis.

Regulatory light chain-a myosin kinase (aMK), which phosphorylates one of the myosin regulatory light chains, RLC-a, contained in the catch muscle of scallop, was also found to phosphorylate heavy chains of scallop myosin. After incubation of myosin isolated from the opaque portion of scallop smooth muscle (opaque myosin) with aMK in the presence of [gamma-32P]ATP, about 2 mol of 32P was incorporated per mol of the myosin. The radioactivity was mostly found in the heavy chain at 0.26 M KCl. The pH-activity curve and MgCl2 requirement for the heavy chain phosphorylation were similar to those for RLC-a phosphorylation. In contrast, the dependency of activity on KCl concentration was different from that for RLC-a. The heavy chain phosphorylation activity decreased with increase in KCl concentration up to 0.06 M, and then increased at concentrations over 0.06 M to a maximum at around 0.26 M KCl. This complicated profile probably reflects the solubility of myosin, and the phosphorylation site may be located in the rod portion insoluble at low KCl concentrations. Phosphorylation of heavy chain did not change the solubility of the opaque myosin molecule at all. The acto-opaque myosin ATPase activity in the presence of Ca2+ was found to be decreased to less than one-fourth by the heavy chain phosphorylation.

Animals↗
PubMed1988

Auditory postauricular responses in patients with peripheral facial nerve palsy.

Auditory postauricular response (PAR) was determined in 52 subjects with normal hearing and 83 patients with unilateral peripheral facial nerve palsy. PAR was induced bilaterally by bilateral aural stimulation in 50 (96%) of the 52 subjects. Determination of PAR in the 83 patients disclosed that the prognosis was significantly (p less than 0.01) better for those in whom PAR occurred within 4 weeks of onset, in comparison with those without PAR. PAR determination was thus considered to be a useful procedure for determining the prognosis of peripheral facial nerve palsy.

Acoustic Stimulation↗
PubMed1987

Regurgitant bile acids and mucosal injury of the gastric remnant after partial gastrectomy.

Three groups, each consisting of seven patients who had undergone either Billroth I, Billroth II, or pylorus-preserving gastrectomies, were evaluated more than 18 months postoperatively in terms of concentration and amount of bile acids in the gastric aspirate and histologic changes in the gastric remnant mucosa. Concentrations of bile acids were determined by gas chromatography and mucosal specimens were obtained by endoscopic biopsy. The total bile acid concentration and all of the individual fractional bile acid levels, whether free or conjugated, were significantly higher in the Billroth II group than in the other two groups. The amount of gastric aspirate was also highest in the Billroth II group. Endoscopic biopsy revealed glandular dysplasia to be predominantly in the Billroth II group. The presence of bile acids in the gastric remnant may contribute to mucosal injury, possibly leading to cancer in the gastric remnant, especially after the Billroth II operation.

Adult↗
PubMed1987

Characterization of regulatory light chain-a myosin kinase from smooth muscle of scallop, Patinopecten yessoensis.

The protein kinase that phosphorylates the regulatory light chain-a (RLC-a) of scallop smooth muscle myosin was isolated from scallop smooth muscle (Sohma, H. & Morita, F. (1986) J. Biochem. 100, 1155-1163). The enzymatic properties of this kinase (aMK) were investigated using RLC-a as the substrate. The Km value for ATP was 6.5 microM in the presence of 27 microM RLC-a at pH 7.0, and that for RLC-a was 133 microM in the presence of 1 mM ATP. The Vm value at saturation of both RLC-a and ATP was 0.25 s-1 at pH 7.0. The pH activity curve for aMK was bell-shaped with a maximum at around pH 7.8. The aMK activity was inhibited strongly by an increase in the KCl concentration. aMK required Mg2+, but was inhibited by high concentrations of Mg2+. The optimum activity was seen at 3 mM MgCl2. The mode of inhibition of the aMK activity by Ca2+ was studied. Assuming that the binding of Ca2+ to aMK induces the inhibition, the dissociation constant of Ca2+ was estimated to be 64 microM. aMK also phosphorylated LC20 of chicken gizzard myosin at a similar rate to that for RLC-a and the DTNB light chain of rabbit skeletal muscle myosin at a more lower rate. The helix and beta-sheet contents of aMK were estimated to be 19 and 30%, respectively, from the CD spectrum.

Amino Acid Sequence↗
PubMed1986

Purification of a protein kinase phosphorylating myosin regulatory light chain-a (RLC-a) from smooth muscle of scallop, Patinopecten yessoensis.

A protein kinase activity phosphorylating regulatory light chain-a (RLC-a) of scallop smooth muscle myosin was found to be present in scallop smooth muscle homogenate. The kinase was purified to homogeneity and named RLC-a myosin kinase (aMK). aMK was extracted from the muscle homogenate with a low salt solution and was purified by successive DE-32 ion exchange chromatography, gel filtration on Ultrogel AcA 44, and affinity chromatography on Sepharose 4B-6-aminohexyl-1-pyrophosphate. The molecular weight of aMK was estimated to be 40-kDa from the mobility on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and 35-kDa from the elution volume on Sephadex G-150 gel filtration. The phosphorylation site of RLC-a by aMK was determined to be Ser residue(s). Only RLC-a was phosphorylated; the other regulatory light chain, RLC-b, was not. The phosphorylatable Ser of RLC-a is, therefore, considered to be Ser-11, which is located in the N-terminal region having a different amino acid sequence from that of RLC-b. RLC-a was phosphorylated by aMK 3 times faster in the free state than in the bound state to myosin. aMK does not require calmodulin and is rather inhibited by CaCl2.

Animals↗
PubMed1985

Phosphorylation of regulatory light chain a (RLC-a) in smooth muscle myosin of scallop, Patinopecten yessoensis.

One of the two regulatory light chains, RLC-a, of scallop smooth muscle myosin was fully phosphorylated by myosin light chain kinase of chicken gizzard muscle. The residue phosphorylated was Ser. It may be the Ser at number 11 from the N-terminal. The sequence of 9 residues around the Ser-11, QRATSNVFA, is identical with that around the phosphorylatable Ser of LC20 of chicken gizzard myosin. RLC-a was also phosphorylated slowly by cAMP-dependent protein kinase. The phosphorylation of RLC-a may be involved in the regulatory system for the catch contraction of scallop muscle.

Animals↗
PubMed1984

[Diagnosis of pituitary microadenoma by magnification carotid angiography and intercavernous sinus venography].

Carotid angiography was performed on 12 cases of pituitary microadenomas at 2.3 X magnified frontal projection and 3.0 X magnified lateral projection. Magnification carotid angiograms were analyzed to determine the pathologic findings in 12 cases on 23 sides. Carotid angiograms demonstrated compressed posterior pituitary gland in 3 of 12 cases and 4 of 23 sides which resulted from the expansion of pituitary microadenomas. But carotid angiogram failed to demonstrate any evidence of tumor stain, abnormal capsular arteries or hypertrophied inferior hypophyseal arteries. These results suggested that magnification carotid angiography was not a useful diagnostic procedure for the detection of pituitary microadenomas. Intercavernous sinus venography was performed on 12 cases of pituitary microadenomas. The technique consisted in catheterization into the inferior petrosal sinus after puncture of the femoral vein. Injection of 10 ml. of contrast medium into the inferior petrosal sinus at a rate of 5 ml. per second. The base projection is most demonstrable and routinely used. Intercavernous sinus venography identified the presence of microadenoma in 10 of 12 cases and false negative in two cases. Nine of 12 cases demonstrated narrowing, interruption and disappearance of the anterior and inferior intercavernous sinuses. Only 3 of 12 cases demonstrated narrowing of the posterior intercavernous sinus and nine cases demonstrated compression signs of the venous strips of the cavernous sinus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1984

Comparison of antimetastatic effect against Lewis lung carcinoma after intratumoral and intravenous injections of cell-wall skeleton of Propionibacterium acnes C7 in C57BL/6 mice.

Antimetastatic activity of cell-wall skeleton of Propionibacterium acnes C7 (P. acnes-CWS) in C57BL/6 mice varied depending on the injection route. The kinetics of antimetastatic effect against Lewis lung carcinoma (3LL) revealed that the sooner intratumoral (it) injection of P. acnes-CWS was carried out, the better the result. However, intravenous (iv) injection of P. acnes-CWS produced the best result if P. acnes-CWS was injected at about the time when metastases began to develop in the lungs. Pretreatment with intrafootpad (ifp) injection of P. acnes-CWS inhibited primary tumor growth and subsequent pulmonary metastases especially when given 7 days before tumor inoculation into the same footpad, but tended to enhance artificial pulmonary metastases when given 7 days before iv injection of tumor cells. In contrast, pretreatment with iv injection of P. acnes-CWS enhanced spontaneous pulmonary metastases especially when given 7 days before ifp inoculation of tumor cells, but inhibited artificial pulmonary metastases when given one day or 7 days before iv injection of tumor cells. These results suggest the difficulty of treatment of tumor metastases with immunological adjuvants. In T-cell-deprived mice, it injection of P. acnes-CWS showed no antimetastatic effect against 3LL, but iv injection was still effective. This indicates that T-cells are required for the antimetastatic effect of it injection of P. acnes-CWS, but iv injection of P. acnes-CWS is able to inhibit pulmonary metastases in T-cell-deprived mice.

Animals↗