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Y Goto

Publications and source records attributed to Y Goto.

At least 19 recordsLinked to original sources
PubMed1992

Charge repulsion in the conformational stability of melittin.

Electrostatic repulsion between positively charged groups has been suggested to be critical in determining the conformation of melittin. To clarify the role of repulsive forces, we prepared a series of succinylated melittins, an acetylated melittin, and a synthetic melittin mutant, with various degrees of charge repulsion. The conformation of the melittin derivatives was examined by far-UV circular dichroism under various conditions of pH and salt at 20 degrees C. The stability of the tetrameric helical state was found to be dependent on the net charge of the peptides. The charge repulsive forces destabilized the helical state of intact melittin by 600 cal/(charge.mol of tetramer). This value was close to the corresponding one (450 cal/(charge.mol)) obtained for the acidic molten globule of horse cytochrome c [Goto, Y., & Nishikiori, S. (1991) J. Mol. Biol. 222, 679-686], which has a molecular weight and a net charge comparable to those of the tetrameric melittin. Small-angle X-ray scattering of the tetrameric melittin and the molten globule of cytochrome c showed that the two states are also comparable to each other in the radius of gyration. These results suggest that the contribution of electrostatic repulsion to the conformational stability of melittin is similar to that of the molten globule.

Amino Acid Sequence↗
PubMed1992

A novel human insulinoma-associated cDNA, IA-1, encodes a protein with "zinc-finger" DNA-binding motifs.

A subtraction library was constructed from human insulinoma (beta cell tumor) and glucagonoma (alpha cell tumor) cDNA phagemid libraries. Differential screening of 153 clones with end-labeled mRNAs from insulinoma, glucagonoma, and HeLa cells resulted in the isolation of a novel cDNA clone designated IA-1. This cDNA clone has a 2838-base pair sequence consisting of an open reading frame of 1530 nucleotides, which translates into a protein of 510 amino acids with a pI value of 9.1 and a molecular mass of 52,923 daltons. At the 3'-untranslated region there are seven ATTTA sequences between two polyadenylation signals (AATAAA). The IA-1 protein can be divided into two domains based upon the features of its amino acid sequence. The NH2-terminal domain of the deduced protein sequence (amino acids 1-250) has four classical pro-hormone dibasic conversion sites and an amidation signal sequence, Pro-Gly-Lys-Arg. The COOH-terminal domain (amino acids 251-510) contains five putative "zinc-finger" DNA-binding motifs of the form X3-Cys-X2-4-Cys-X12-His-X3-4-His-X4 which has been described as a consensus sequence for members of the Cys2-His2 DNA-binding protein class. Northern blot analysis revealed IA-1 mRNA in five of five human insulinoma and three of three murine insulinoma cell lines. Expression of this gene was undetectable in normal tissues. Additional tissue studies revealed that the message is expressed in several tumor cell lines of neuroendocrine origin including pheochromocytoma, medullary thyroid carcinoma, insulinoma, pituitary tumor, and small cell lung carcinoma. The restricted tissue distribution and unique sequence motifs suggest that this novel cDNA clone may encode a protein associated with the transformation of neuroendocrine cells.

Amino Acid Sequence↗
PubMed1992

Synergism in insulin-like effects of molybdate plus H2O2 or tungstate plus H2O2 on glucose transport by isolated rat adipocytes.

The effect of molybdate, tungstate, molybdate plus H2O2 or tungstate plus H2O2 on 3-O-methylglucose (3-O-MG) uptake was studied in isolated rat adipocytes to investigate whether these agents possess an insulin-like action. High concentrations (10-30 mM) of molybdate or tungstate significantly stimulated the uptake of 3-O-MG while 1 mM of the metaloxides did not. The combination of 1 mM molybdate and 1 mM H2O2, or 1 mM tungstate and 1 mM H2O2 induced striking stimulation of the uptake of 3-O-MG in a synergistic manner, whereas 1 mM H2O2 alone showed only a small effect. The effect of metaloxides plus H2O2 (1 mM) and the effect of insulin (20 nM) were not additive, and both effects were ATP or energy dependent based on experiments using KCN. These results indicate that a weak insulin-like effect of molybdate or tungstate is potentiated synergistically with H2O2, presumably by producing peroxocompounds. Based on the present findings, these new agents may be useful for investigating the mechanism of insulin action and may indicate a new class of drugs for diabetes mellitus.

3-O-Methylglucose↗
PubMed1992

Fusion of phospholipid vesicles induced by an amphiphilic model peptide: close correlation between fusogenicity and hydrophobicity of the peptide in an alpha-helix.

A model peptide with 51 amino acid residues consisting of tandem repeats of a Lys-Lys-Leu-Leu sequence and a turn sequence of Asn-Pro-Gly at the center of the molecule has a random conformation at neutral pH but adopts an amphiphilic alpha-helical form in the presence of various salts or nucleotides [Goto, Y., & Aimoto, S. (1991) J. Mol. Biol. 218, 387-396; Goto, Y., Okamura, N., & Aimoto, S. (1991) J. Biochem. (Tokyo) 109, 746-750]. The interaction of this model peptide with liposome membranes and the resulting alpha-helical conformational transition and membrane fusion as well as the effect of the nucleotide ATP on these events were examined at neutral pH. The peptide associated stoichiometrically with liposome membranes composed of phosphatidylserine (PS) and phosphatidylcholine (PC) in a molar ratio of 2:1, resulting in formation of an amphiphilic alpha-helix and induction of fusion of the liposomes. However, the final fusion level was not correlated with the amount of binding or the helix content and was found to increase on an increase in hydrophobicity of the peptide in the alpha-helical form by neutralization of its positive charges by the negative charges of PS. In contrast, in the presence of ATP, the peptide bound completely to the PS/PC membranes at a lower concentration of liposome and concomitantly induced membrane fusion, indicating that ATP cooperates with PS to neutralize the charges of the peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Brefeldin A-resistant mutants of human epidermoid carcinoma cell line with structural changes of the Golgi apparatus.

We have isolated brefeldin A (BFA)-resistant cell lines, KB/BF-1 and KB/BF-2, from the human epidermoid carcinoma KB cell line. The BFA-resistant phenotypes have been stably maintained for more than 3 months in the absence of BFA. KB/BF-1 and KB/BF-2 showed 10-30-fold higher resistance to cytotoxicity of BFA but were 2-3-fold more sensitive to monensin and nigericin, than KB cells. KB/BF-1 showed aberrant structures of the Golgi complex with poorly developed cisternae surrounded by many small vesicles. Immunocytochemical studies were done with antibodies against a Golgi-specific antigen (chronic rheumatoid arthritis antigen) and a coatomer subunit (beta-subunit for coat proteins of non-clathrin-coated vesicles). Golgi-specific markers were distributed into the small vesicles which were localized diffusedly in cytoplasm of KB/BF-1 cells. Such Golgi markers were observed in a strictly confined perinuclear region of the parental KB cells, whereas in the mutant cells the markers were distributed more diffusedly in dot-like structures at perinuclear regions. In addition, when exposed to BFA, the mutant and parental cells showed a different distribution of these markers. Synthesis and maturation of low density lipoprotein receptor showed apparently slower rates in processing of low density lipoprotein receptor in KB/BF-1 and KB/BF-2 cells than those observed in their parental KB cells. Protein secretion in KB/BF-1 and KB/BF-2 cells was about 30% less than that in KB cells. Much less inhibition by BFA on the secretion was observed in KB/BF-1 and KB/BF-2 cells. A BFA-resistant mutation in BFA-resistant KB cell lines appears to affect assembly of the Golgi apparatus as well as some Golgi-specific functions.

Brefeldin A↗
PubMed1992

In vivo and in vitro effects of cyclosporin A on glucose transport by soleus muscles of mice.

The effect of cyclosporin A (CyA) on 2-deoxyglucose (2DG) uptake by soleus muscles of ICR mice was studied in vivo and in vitro. The basal and insulin-stimulated uptakes of 2DG by the muscles as well as the plasma insulin level were significantly decreased by the in vivo treatment of mice with 20 mg/kg/day of CyA for 6 weeks (P less than 0.01 and P less than 0.05), whereas the insulin binding was increased inversely in the muscles from 20 mg/kg/day CyA-treated mice. The insulin-stimulated uptake of 2DG by the muscles was significantly decreased by the in vitro treatment of the muscles with 1, 10 and 100 micrograms/mL of CyA (P less than 0.05 and P less than 0.01, respectively), while the basal uptake of 2DG was not changed by the in vitro treatment of the muscles with CyA. The insulin binding to the muscles was not altered by the in vitro treatment of the muscles with CyA. These findings suggest that CyA affects not only the insulin secretion from the pancreatic islets but also the postbinding mechanisms of insulin action on the glucose transport by the muscles, which may account for a part of the diabetogenic effect of CyA.

Adenosine Triphosphate↗
PubMed1992

[Long-term treatment of acromegaly and gigantism with octreotide (SMS 201-995)].

Twenty-one patients with active acromegaly and two patients with pituitary gigantism were treated with the long-acting somatostatin analogue octreotide (100-600 micrograms/day, sc, two or three times daily or 300-1500 micrograms daily by intermittent sc infusion) for 9-63 months. There was rapid clinical improvement. The fasting plasma GH levels were significantly suppressed (less than 50% of the values before treatment) in 17 patients and were normalized (less than 5 ng/ml) in 6 patients (27.3%). Plasma IGF-I levels were lowered by 50% and were normalized in 7 out of 18 cases. The effect of octreotide on pituitary tumor size was evaluated in 13 patients. In 4 cases, the shrinkage of the pituitary tumor was detected by computed tomographic scans and/or magnetic resonance imaging studies. The drug was generally well tolerated. However, there were probably newly formed gallstones in two patients during the therapy. Our study suggests that octreotide is an effective and relatively safe new approach for treating active acromegaly and gigantism.

Acromegaly↗
PubMed1992

Epidermal cell differentiation inhibitor ADP-ribosylates small GTP-binding proteins and induces hyperplasia of epidermis.

Epidermal cell differentiation inhibitor (EDIN) is a recently discovered protein which inhibits terminal differentiation of cultured keratinocytes (Sugai, M., Enomoto, T., Hashimoto, K., Matsumoto, K., Matsuo, Y., Ohgai, H., Hong, Y.-M., Inoue, S., Yoshikawa, K., and Suginaka, H. (1990) Biochem. Biophys. Res. Commun. 173, 92-98). The amino acid sequenced deduced from the EDIN gene has revealed that EDIN shares high amino acid sequence homology with the exoenzyme C3 of Clostridium botulinum (Inoue, S., Sugai, M., Murooka, Y., Paik, S.-Y., Hong, Y.-M., Ohgai, H., and Suginaka, H. (1991) Biochem. Biophys. Res. Commun. 174, 459-464), which has been shown to ADP-ribosylate the rho/rac proteins (members of the small GTP-binding protein family). We show here that EDIN ADP-ribosylates rhoB p21 in time- and dose-dependent manners in a cell-free system. Kinetic studies of the ADP-ribosylation and peptide mapping of the reaction products of rhoB p21 by EDIN and C3 suggest that the mode of action of the ADP-ribosylation by EDIN is quite similar to that by C3 and that the ADP-ribosylation site of rhoB p21 by EDIN is presumably the same as that by C3. Proteins in epidermal membranes and keratinocyte homogenate with Mr values of about 22,000 are ADP-ribosylated by EDIN or C3. Treatment of cultured human keratinocytes by EDIN or C3 results in an inhibition of terminal differentiation and a stimulation of growth of the cells. Moreover, EDIN and C3 injected into adult mouse skin induce hyperplasia of epidermis. These results suggest that EDIN and C3 affect growth and differentiation of keratinocytes by ADP-ribosylation of protein(s) with a Mr of about 22,000, which may be the rho/rac proteins or related proteins.

Adenosine Diphosphate Ribose↗
PubMed1992

Mechanism of the conformational transition of melittin.

It is known that, while melittin at micromolar concentrations is unfolded under conditions of low ionic strength at neutral pH, it adopts a tetrameric alpha-helical structure under conditions of high ionic strength, at alkaline pH, or at high peptide concentrations. To understand the mechanism of the conformational transition of melittin, we examined in detail the conformation of melittin under various conditions by far-UV circular dichroism at 20 degrees C. We found that the helical conformation is also stabilized by strong acids such as perchloric acid. The effects of various acids varied largely and were similar to those of the corresponding salts, indicating that the anions are responsible for the salt- or acid-induced transitions. The order of effectiveness of various monovalent anions was consistent with the electroselectivity series of anions toward anion-exchange resins, indicating that the anion binding is responsible for the salt- or acid-induced transitions. From the NaCl-, HCl-, and alkaline pH-induced conformational transitions, we constructed a phase diagram of the anion- and pH-dependent conformational transition. The phase diagram was similar in shape to that of acid-denatured apomyoglobin [Goto, Y., & Fink, A.L. (1990) J. Mol. Biol. 214, 803-805] or that of the amphiphilic Lys, Leu model polypeptide [Goto, Y., & Aimoto, S. (1991) J. Mol. Biol. 218, 387-396], suggesting a common mechanism of the conformational transition. The anion-, pH-, and peptide concentration-dependent conformational transition of melittin was explained on the basis of an equation in which the conformational transition is linked to proton and anion binding to the titratable groups.

Anions↗
PubMed1992

A novel point mutation in the mitochondrial tRNA(Leu)(UUR) gene in a family with mitochondrial myopathy.

A T-to-C transition mutation at nucleotide position 3,250 in the mitochondrial tRNA(Leu)(UUR) gene was present in a family with mitochondrial myopathy. Two of three muscle biopsies examined had complex I (NADH-ubiquinone oxidoreductase) deficiency. Heteroplasmy of wild and mutant mitochondrial DNA was detected by Nae I digestion of the polymerase chain reaction products with a modified primer. This was found in blood or muscle samples or both from all seven members examined. Similar to the 3,243 mutation in most patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes), the new mutation site was located in the dihydrouridine loop and embedded in the binding region of mitochondrial transcription termination factor. Elucidation of the effects of this mutation may help clarify the role of mitochondrial tRNAs and transcription termination.

Base Sequence↗
PubMed1992

A case of accessory mitral valve leaflet associated with solitary mitral cleft.

Accessory mitral valve leaflet is a rare congenital anomaly. More than half of the cases show other congenital cardiac defects and almost all of the cases show subaortic obstruction. We report a case of an accessory mitral valve tissue without outflow obstruction associated with mitral cleft of the posterior mitral leaflet. To our knowledge, this is the first reported case of the combination of these two congenital anomalies.

Adult↗
PubMed1992

Segmental cytochrome c-oxidase deficiency in CPEO: teased muscle fiber analysis.

In an attempt to elucidate the pathogenesis of focal cytochrome c-oxidase (COX) deficiency in skeletal muscle from patients with chronic progressive external ophthalmoplegia (CPEO), we examined the longitudinal distribution of COX activity in single muscle fibers from 6 CPEO patients with muscle mitochondrial DNA (mtDNA) deletions. A new method for teasing single muscle fibers, recently developed in our laboratory, revealed fibers with COX-positive and -negative segments in all 6 patients. The borders between the enzyme-positive and -negative segments in these fibers were sharply delineated, so that the length of each COX-negative segments could be accurately measured. The proportion of the sum of the lengths of the enzyme-negative segments to the total length of the muscle fibers correlated well with the proportion of deleted mtDNA, suggesting that abnormal mitochondria harboring mutant mtDNA may be responsible for the focal loss of COX activity.

Adolescent↗
PubMed1992

An experimental model of mitochondrial myopathy: germanium-induced myopathy and coenzyme Q10 administration.

In skeletal muscles from rats treated with germanium for 23 weeks, there were numerous ragged-red fibers and cytochrome-c oxidase (COX)-deficient fibers. Biochemically, germanium reduced the enzyme activities in the mitochondrial respiratory chain. Rotenone-sensitive NADH-cytochrome-c reductase as well as COX activities were markedly reduced, while succinate-cytochrome-c reductase was less severely, but significantly, affected. The histopathological findings in these muscles were similar to those seen in patients with mitochondrial encephalomyopathy, suggesting that germanium-induced myopathy may be a useful experimental model. Coenzyme Q10 administration appeared to be ineffective in preventing this experimental myopathy.

Animals↗
PubMed1992

Ejecting volume, filling volume and stroke volume gains: new indexes of inotropism and lusitropism.

We propose new indexes to evaluate the effects of ventricular inotropism and lusitropism on stroke volume. The end-systolic pressure-volume relationship (ESPVR) or its slope (Emax) has been employed to assess ventricular inotropism. The end-diastolic pressure-volume relationship (EDPVR) or compliance has been used to express ventricular diastolic properties or lusitropism. However, their net effect on stroke volume under a given set of preload and afterload pressures has not quantitatively been evaluated. Ejecting volume gain (Ge) was proposed to quantify the inotropic effect on stroke volume by the change in end-systolic volume between the two ESPVR curves obtained before and during an inotropic intervention at a specified ejecting pressure. Ge is a function of afterload pressure. Filling volume gain (Gf) was proposed to quantify the lusitropic effect on stroke volume by the change in end-diastolic volume between the two EDPVR curves before and during a lusitropic intervention at a specified filling pressure. Gf is a function of preload pressure. The net effect of these inotropic and lusitropic effects on stroke volume at these specified preload and afterload pressures can be expressed by the sum of Ge and Gf. We call this sum stroke volume gain (Gsv). Gsv is a function of preload and afterload pressures. Using representative examples, we demonstrate that these new indexes are conceptually useful to quantitatively understand changes in the pumping ability of the heart under simultaneous inotropic and lusitropic effects as a function of ejecting and filling pressures.

Animals↗
PubMed1992

Cardiac muscle fiber force versus length determined by a cardiac muscle crossbridge model.

A mathematical model incorporating Huxley's sliding filament crossbridge muscle model coupled with parallel and series elastic components was simulated to examine force-length relations under different external calcium concentrations. Several researchers have determined experimentally in both papillary muscle preparations and in situ heart experiments that the calcium concentration (or effective concentration from inotropic agents) will affect the strength and convexity of the cardiac muscle fiber force-length relations. Simulations were performed over a several-order-of-magnitude range of calcium concentrations in isometric contractions and these showed that the force-length curve convexity was changed. Simulation results demonstrated that increasing the stiffness in the model contractile element or series elasticity element did not change the force-length convexity. Increasing the series elasticity element stiffness did slightly change the shape of the force-length curve. The model predicts that the curve convexity changes as a result of the calcium-troponin interactions.

Calcium↗
PubMed1992

Epinephrine and calcium have similar oxygen costs of contractility.

We compared the oxygen cost of increasing ventricular contractility using Emax (slope of the ventricular end-systolic pressure-volume relation) as the index of ventricular contractility. Contractility was enhanced by calcium and epinephrine in paired experiments on dog left ventricles. Firstly, we obtained left ventricular oxygen consumption (VO2) and systolic pressure-volume area (PVA, a measure of total mechanical energy) of contractions at different volumes in the control contractile state to determine a reference VO2-PVA relation. PVA was obtained as the area in the pressure-volume (P-V) diagram which was bounded by the end-systolic P-V line, end-diastolic P-V curve and systolic P-V trajectory of individual contractions. Secondly, we gradually enhanced Emax with calcium and epinephrine in two consecutive runs at a fixed ventricular volume. Both VO2 and PVA increased with enhanced Emax. From these VO2-PVA data, we calculated the PVA-independent VO2 values at the respective enhanced Emax levels and determined the oxygen cost of Emax as the slope of the relation between the PVA-independent VO2 and Emax. The cost per beat and per 100 g was 0.00158 ml O2/(mmHg/ml) for calcium and 0.00166 ml O2/(mmHg/ml) for epinephrine on average, values not significantly different from each other (P less than 0.05). We conclude that epinephrine and calcium have similar oxygen costs of contractility over a wide range of Emax despite their different pharmacological mechanisms of positive inotropism.

Animals↗
PubMed1992

Similar oxygen cost of myocardial contractility between DPI 201-106 and epinephrine despite different subcellular mechanisms of action in dog hearts.

The effects of DPI 201-106 (a novel, cyclic AMP-independent positive inotropic agent with Ca(2+)-sensitizing and Na(+)-channel agonistic mechanisms) on myocardial mechanics and energetics were assessed in the excised cross-circulated dog left ventricle. In the first protocol, the relation between left ventricular oxygen consumption (VO2) and systolic pressure-volume area (PVA) was analyzed before and during administration of DPI 201-106. The reciprocal of the slope of the VO2-PVA relation has been shown to reflect the contractile efficiency, and the VO2-intercept consists of the oxygen cost of contractility-dependent excitation-contraction coupling and basal metabolism. DPI 201-106 increased Emax (contractility index) and elevated the VO2-PVA relation in a parallel manner, i.e., the VO2-intercept increased without a change in the slope. In the second protocol, the increase in the VO2-intercept of the VO2-PVA relation for a unit increase in Emax (i.e., oxygen cost of enhanced contractility) was compared between DPI 201-106 and epinephrine in a paired manner in each heart. Epinephrine significantly abbreviated the time to end systole, whereas DPI 201-106 did not, suggesting that the mechanism of inotropic action differed between the two drugs. However, the oxygen cost of enhanced contractility was the same between the two drugs in each heart. Therefore, DPI 201-106 did not alter the contractile efficiency nor spare the oxygen cost of enhanced contractility as compared to epinephrine under the present experimental conditions. This suggests that the Ca(2+)-sensitizing effect of DPI 201-106, if any, is too small to spare the oxygen cost of contractility in the blood-perfused, non-failing dog heart.

Animals↗