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F Tokunaga

Publications and source records attributed to F Tokunaga.

At least 145 records · Page 8Linked to original sources
PubMed1987

Lipopolysaccharide-sensitive serine-protease zymogen (factor C) of horseshoe crab hemocytes. Identification and alignment of proteolytic fragments produced during the activation show that it is a novel type of serine protease.

The horseshoe crab clotting factor, factor C, present in the hemocytes is a serine-protease zymogen activated with lipopolysaccharide. It is a two-chain glycoprotein (Mr = 123,000) composed of a heavy chain (Mr = 80,000) and a light chain (Mr = 43,000) [T. Nakamura et al. (1986) Eur. J. Biochem. 154, 511-521]. In our continued study of this zymogen, we have now also found a single-chain form of factor C (Mr = 123,000) in the hemocyte lysate. The heavy chain had the NH2-terminal sequence of Ser-Gly-Val-Asp-, consistent with that of the single-chain factor C, indicating that the heavy chain is derived from the NH2-terminal part of the molecule. The light chain had an NH2-terminal sequence of Ser-Ser-Gln-Pro-. Incubation of the two-chain zymogen with lipopolysaccharide resulted in the cleavage of a Phe-Ile bond between residues 72 and 73 of the light chain. Concomitant with this cleavage, the A (72 amino acid residues) and B chains derived from the light chain were formed. The complete amino acid sequence of the A chain was determined by automated Edman degradation. The A chain contained a typical segment which is similar in sequence to a family of repeats in human beta 2-glycoprotein I, complement factors B, protein H, C4b-binding protein, and coagulation factor XIII b subunit. The NH2-terminal sequence of the B chain was Ile-Trp-Asn-Gly-. This chain contained the serine-active site sequence-Asp-Ala-Cys-Ser-Gly-Asp-Ser-Gly-Gly-Pro-. These results indicate that horseshoe crab factor C exists in the hemocytes in a single-chain zymogen form and is converted to an active serine protease by hydrolysis of a specific Phe-Ile peptide bond.

Amino Acid Sequence↗
PubMed1987

Complete nucleotide sequence of cDNA and deduced amino acid sequence of rat liver arginase.

Arginase (EC 3.5.3.1) catalyzes the last step of urea synthesis in the liver of ureotelic animals. The nucleotide sequence of rat liver arginase cDNA, which was isolated previously (Kawamoto, S., Amaya, Y., Oda, T., Kuzumi, T., Saheki, T., Kimura, S., and Mori, M. (1986) Biochem. Biophys. Res. Commun. 136, 955-961) was determined. An open reading frame was identified and was found to encode a polypeptide of 323 amino acid residues with a predicted molecular weight of 34,925. The cDNA included 26 base pairs of 5'-untranslated sequence and 403 base pairs of 3'-untranslated sequence, including 12 base pairs of poly(A) tract. The NH2-terminal amino acid sequence, and the sequences of two internal peptide fragments, determined by amino acid sequencing, were identical to the sequences predicted from the cDNA. Comparison of the deduced amino acid sequence of the rat liver arginase with that of the yeast enzyme revealed a 40% homology.

Amino Acid Sequence↗
PubMed1987

Demonstration of rod and cone photoreceptors in the lamprey retina by freeze-replication and immunofluorescence.

In common with other cyclostomata, the Japanese river lamprey (Lampetra japonica) has a retina consisting of distinct types of photoreceptor cells called long and short photoreceptor cells. After freeze-fracture, disc membranes of these photoreceptor cells were characterized in common by a homogeneous distribution of intramembrane particles on the protoplasmic fracture faces, in contrast to those of the myeloid bodies bearing scattering particles. Immunofluorescent examination was applied to the retina with monoclonal antibodies raised against bovine and chicken rhodopsins. Positive immunoreactivity was found to be limited to outer segments of the short cell, leaving the entire body of the long cell and all other components of the retina negative. The results suggest that the short cell is more closely related to a rod-type photoreceptor cell characterized by rhodopsin as its visual pigment.

Animals↗
PubMed1987

Purification and amino acid sequence of Kunitz-type protease inhibitor found in the hemocytes of horseshoe crab (Tachypleus tridentatus).

A low molecular weight protein protease inhibitor was purified from Japanese horseshoe crab (Tachypleus tridentatus) hemocytes. It consisted of a single polypeptide with a total of 61 amino acid residues. This protease inhibitor inhibited stoichiometrically the amidase activity of trypsin (Ki = 4.60 X 10(-10) M), and also had inhibitory effects on alpha-chymotrypsin (Ki = 5.54 X 10(-9) M), elastase (Ki = 7.20 X 10(-8) M), plasmin, and plasma kallikrein. However, it had no effect on T. tridentatus clotting enzyme and factor C, mammalian blood coagulation factors (activated protein C, factor Xa and alpha-thrombin), papain, and thermolysin. The complete amino acid sequence of this inhibitor was determined and its sequence was compared with those of bovine pancreatic trypsin inhibitor (BPTI) and other Kunitz-type inhibitors. It was found that the amino acid sequence of this inhibitor has a high homology of 47 and 43% with those of sea anemone inhibitor 5-II and BPTI, respectively. Thus, this protease inhibitor appeared to be one of the typical Kunitz-type protease inhibitors.

Amino Acid Sequence↗
PubMed1987

Primary structure of anti-lipopolysaccharide factor from American horseshoe crab, Limulus polyphemus.

The complete amino acid sequence of anti-lipopolysaccharide (LPS) factor purified from the hemocytes lysate of the American horseshoe crab, Limulus polyphemus, was determined by characterization of the NH2-terminal sequence and the peptides generated after digestion of the protein with lysyl endopeptidase, clostripain, and Staphylococcus aureus V8 protease. Upon sequencing the peptides by the automated Edman method, the following primary structure was obtained: (Sequence: in text). During the sequence analysis, two species of the protein, which differed from each other at one locus, were found and characterized. L. polyphemus anti-LPS factor was a basic protein consisting of a single polypeptide chain of 101 residues and a calculated molecular weight of 11,786 or 11,800. The hydrophobic NH2-terminal sequence and the clustering of positive charges found in the disulfide loop yielded a typical amphipathic character of this protein. Moreover, L. polyphemus anti-LPS factor showed 83% sequence identity with the Tachypleus tridentatus protein, and the sequence similar to that observed in the EF-hand structure was found to contain in the COOH terminal portions of these proteins, although its function is unknown.

Amino Acid Sequence↗
PubMed1985

Interaction of tyrosine residues with the chromophore in bacteriorhodopsin.

We previously reported that the absorption spectrum at low temperatures of iodinated bacteriorhodopsin can be separated into four components with maxima at shorter wavelengths than in native bacteriorhodopsin. In this study, the time course of the formation of each spectral component after iodination was analyzed, revealing that these four components correspond to four different iodinated states of tyrosine residues interacting with the retinal chromophore of bacteriorhodopsin. Therefore at least two tyrosine residues interact with the chromophore of bacteriorhodopsin.

Bacteriorhodopsins↗
PubMed1984

Photochemical reaction of 7,8-dihydrorhodopsin at low temperatures.

The photoreaction of 9-cis-7,8-dihydrorhodopsin was examined at liquid nitrogen temperatures (-180 degrees C) in order to elucidate the photochemical events in visual pigments. This rhodopsin analog was prepared by incubating 9-cis-7,8-dihydroretinal with bovine opsin in the dark. 9-cis-7,8-Dihydrorhodopsin (lambda max = 427 nm) was cooled to -180 degrees C, and then irradiated at -180 degrees C with a 390 nm light, resulting in formation of its bathochromic product (lambda max = 465 nm). This result indicates that the presence of four double-bonds adjacent to the Schiff base nitrogen is sufficient to allow formation of a bathochromic product. Thus, the mechanism of formation of bathorhodopsin (in bovine rhodopsin system) may be considered as some change of the interaction between the conjugated double-bond system from C-9 to the Schiff base nitrogen and its surrounding charges in opsin, caused by rotation of 11-12 double-bond.

Animals↗
PubMed1983

Isolation and nucleotide sequence of a partial cDNA clone for bovine opsin.

Bovine cDNAs were cloned by using a mixture of 18-base-long synthetic deoxyribonucleotides as a hybridization probe. The longest cDNA clone (pBO-1) contained an 811-bp insert that included the 434 bp of the coding region corresponding to the C-terminal 144 amino acid residues of opsin peptide and the 377 bp of the 3'-untranslated region. The size of opsin mRNA was determined as 23 S by Northern blot hybridization. Bovine liver DNA gave rise to a single band of 2.8 kb, 1.1 kb and 7.9 kb each with Eco RI, Hind III and Bam HI, respectively, by Southern blot hybridization with pBO-1 as probe. Therefore, bovine opsin gene may occur once per haploid genome.

Amino Acid Sequence↗
PubMed1983

Two forms of intermediates of frog rhodopsin in rod outer segments.

Using frog rod outer segments, we measured changes of the absorption spectrum during the conversion of rhodopsin to a photosteady-state mixture composed of rhodopsin, isorhodopsin and bathorhodopsin by irradiation with blue light (440 nm) at -190 degrees C and during the reversion of bathorhodopsin to a mixture of rhodopsin and isorhodopsin by irradiation with red light (718 nm) at -190 degrees C. The reaction kinetics was expressed by one exponential in the former case and by two exponentials in the latter. These results suggest that rhodopsin is composed of a single molecular species, while bathorhodopsin is composed of two kinds of molecular species designated as batho1-rhodopsin and batho2-rhodopsin. On warming the two forms of bathorhodopsin, each bathorhodopsin converted to its own lumirhodopsin, metarhodopsin I and finally a free all-trans-retinal plus opsin. The absorption spectra of the two forms of bathorhodopsin, lumirhodopsin and metarhodopsin I were measured at -190 degrees C. We infer that a rhodopsin molecule in the excited state relaxes to either batho1-rhodopsin or batho2-rhodopsin, and then converts to its own intermediates through one of the two parallel pathways.

Animals↗
PubMed1982

Botryoid rhabdomyosarcoma of the gallbladder in a child.

The first case of botryoid rhabdomyosarcoma of the gallbladder in a child is described and compared with previously reported cases from the world literature. Despite its rarity, rhabdomyosarcoma of the liver and biliary system should be considered when an obstructive jaundice is seen in children. Radical surgery with additional chemotherapy and radiotherapy are necessary for long-term survival.

Adolescent↗
PubMed1982

Photoreaction of tyrosine-iodinated bacteriorhodopsin at low temperature.

To elucidate the role of tyrosine residues in the shift of lambda max and the light-driven proton pump of bacteriorhodopsin, the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4-5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and it was stable in the dark for several hours at -65 degrees C. Four batho-intermediates were formed by irradiation with green light (500 nm) at -170 degrees C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at -170 degrees C. Four corresponding meta-intermediates were also formed by irradiation at -60 degrees C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.

Bacteriorhodopsins↗
PubMed1982

Electron microscopic observation on phase transition of purple membrane.

Structural changes during the thermal phase transition of purple membrane were observed by freeze-fracture electron microscopy. Native Halobacterium halobium cells contain broad purple membrane areas about 1 micron in diameter. The boundary separating purple and red membranes is obvious. On warming at 80 degrees C, particles of red membrane spread out beyond the boundary. Then a purple membrane area is eventually divided into small areolae of similar size, about 0.1 micron in diameter. By cooling down slowly, the purple membrane area is reformed and the crystalline arrangement also restored.

Bacteriorhodopsins↗
PubMed1980

Circular dichroism of cattle rhodopsin and bathorhodopsin at liquid nitrogen temperatures.

The photoevent in vision has been considered to be the conversion of rhodopsin to bathorhodopsin, which is caused by photoisomerization of the chromphoric retinal. Recently some objections were raised to this hypothesis. The reliability of the hypothesis was verified by measurement of circular dichroism of bathorhodopsin. The measurement of circular dichroism of rhodopsin extract (containing 66% or 75% of glycerol) at liquid nitrogen temperatures (-195 degrees C) by a conventional spectropolarimeter induced an extraordinary large signal, owing to linear dichroism originated from conversion of rhodopsin to bathorhodopsin by the measuring light. The similar linear dichrolism can be induced by irradiation of rhodopsin extract at -195 degrees C with polarized light or natural light. At photosteady state the linear dichroism disappeared. Circular dichroism spectrum of cattle rhodopsin displayed two positive peaks ([theta]max = 80 800 degrees at 335 nm, and [theta]max = 42 600 degrees at 500 nm) at -195 degrees C, whereas, bathorhodopsin displayed a positive peak ([theta]max = 43 100 degrees at 334 nm) and a negative peak ([theta]max = 163 000 degrees at 540 nm). The change of the positive sign to negative one at alpha-band of circular dichroism spectrum supports the hypothesis that the conversion of rhodopsin is due to rotation of the chromophoric retinal about C-11--12 double bond ('photoisomerization model').

Animals↗