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Biomedical subjects

A Ikai

Publications and source records attributed to A Ikai.

At least 127 records · Page 7Linked to original sources
PubMed1984

Isolation and characterization of a high molecular weight actin-binding protein from Physarum polycephalum plasmodia.

A high molecular weight actin-binding protein was isolated from the Physarum polycephalum plasmodia. The protein ( HMWP ) shares many properties with other high molecular weight actin-binding proteins such as spectrin, actin-binding protein from macrophages, and filamin. It has a potent activity to cross-link F-actin into a gel-like structure. Its cross-linking activity does not depend on calcium concentrations. Hydrodynamic studies have revealed that the protein is in the monomeric state of a polypeptide chain with molecular weight of approximately 230,000 in a high ionic strength solvent, while it self-associates into a dimer under physiological ionic conditions. Electron microscopic examinations of HMWP have shown that the monomer particle observed in a high ionic strength solvent is rod shaped with the two-stranded morphology very similar to that of spectrin. On the other hand, under physiological ionic conditions, the HMWP dimer shows the dumb-bell shape with two globular domains connected with a thin flexible strand.

Actins↗
PubMed1983

Alpha-2-macroglobulin-like protease inhibitor from the egg white of cuban crocodile (Crocodylus rhombifer).

A high molecular weight protease inhibitor was purified from the egg white of Cuban crocodile (Crocodylus rhombifer). It inhibited the casein hydrolyzing activity of trypsin, subtilisin and papain. Its native molecular weight was 730,000 and it consisted of four subunits of equal molecular weight, each pair of which were disulfide bonded. The amino acid composition, circular dichroic spectrum and electron micrographs of this protein are also presented. Upon incubation with trypsin this protein yielded a fragment of Mr = 80,000, similar in size to the one known to originate from alpha 2-macroglobulin under the same conditions. The molecular parameters of this protein and the broad inhibitory activity towards thiol and serine proteases with different substrate specificities suggest that it is a protein closely related to alpha 2-macroglobulin in mammalian serum. From its native molecular weight and amino acid composition we believe that this protein is also a reptilian counterpart of the avian ovomacroglobulin described by Miller and Feeney (3).

Alligators and Crocodiles↗
PubMed1983

Analysis of apolipoproteins B100 and B48 by sodium dodecyl sulfate polyacrylamide gradient gel electrophoresis.

Apolipoproteins B100 and B48 in human and rat plasma were studied by using sodium dodecyl sulfate (SDS) polyacrylamide gradient gel electrophoresis. On SDS gradient gel electrophoresis, human and rat apoprotein B100 co-migrated and had an apparent Mr equal 258,000 +/- 12,000. Human and rat apoprotein B48 had an apparent Mr equal 189,000 +/- 6,000. The molecular weight of human apoprotein B100 determined by sedimentation equilibrium analysis was 270,000 +/- 20,000, which was similar to the value determined by SDS gradient gel electrophoresis. However, on SDS polyacrylamide gel electrophoresis at constant concentration, the relative migration value of human apoprotein B100 was not constant when the concentration of polyacrylamide was changed. These results indicate that SDS gradient gel electrophoresis is more suitable for the analysis of apolipoprotein B's than ordinary SDS polyacrylamide gel electrophoresis.

Animals↗
PubMed1982

Structure of bacterial fatty acid synthetase from Brevibacterium ammoniagenes.

Hydrodynamic measurements and a cross-linking study with dimethyl suberimidate have shown that the native fatty acid synthetase from Brevibacterium ammoniagenes is a hexameric protein having a molecular weight of 1.56 . 10(6). The subunits of the enzyme are identical in size (Mr 2.6 . 10(5). The negatively stained fatty acid synthetase had an electron microscopic image of ellipsoidal structure with major and minor axes approximately equal to 270 A and 180 A, respectively. The electron microscopic image is similar to that of the yeast enzyme, which is quite distinct from the B. ammoniagenes enzyme with respect to the subunit composition. The inactivated enzyme prepared by dialysis against a lower ionic strength solution was partially reactivated by raising the ionic strength. Ellipsoidal images similar to those of the native enzyme were found in the electron micrograph of the reactivated enzyme. Sucrose density gradient centrifugation of the reactivated enzyme sample showed that the active component had almost the same sedimentation coefficient as the native hexamer. These results indicate that the enzyme is active only in its hexameric state.

Amino Acids↗
PubMed1982

Hen egg white ovomacroglobulin has a protease inhibitory activity.

Hen egg white ovomacroglobulin purified by Miller and Feeney without reference to its activity was shown to have a protease inhibitory activity towards trypsin, papain, and thermolysin. It has four subunits of equal molecular weight (175,000 by SDS-PAGE) and each two of which are disulfide bonded. Upon incubation with trypsin it yields a fragment of Mr = 80,000 plus smaller ones. The subunit composition, amino acid composition and a newly found protease inhibitory activity place ovomacroglobulin as a closely related protein to human serum alpha 2-macroglobulin.

Amino Acids↗
PubMed1980

Extraction of the apo B cluster from human low density lipoprotein with Tween 80.

The interaction of human serum low density lipoprotein with a non-ionic detergent, Tween 80, was investigated by sedimentation velocity measurements and Sepharose CL-4B gel chromatography. The properties of Tween 80-extracted apoprotein (apo B) were studied by sedimentation velocity and sedimentation equilibrium measurements, gel chromatography, electron microscopy and chemical cross-linking. Tween 80, at low concentrations, increased the sedimentation coefficient of LDL in 3% NaCl to a plateau value. At the same time, the effective Stokes radius of LDL expressed as the partition coefficient in gel chromatography became larger. The effect was reversed in part after protease treatment. A further increase of Tween 80 concentration caused the all-or-none dissociation of the entire mass of apo B from LDL. The remaining lipid core of LDL was not destroyed by detergent at 25 degrees C, but it was at 35 degrees C. The Tween 80-extracted apo B was purified by gel chromatography and its molecular weight and partial specific volume were determined by sedimentation equilibrium analysis in H2O and D2O buffers. It formed a complex of 1,200,000 molecular weight with Tween 80, with f/fo = 2.2. The molecular weight of the protein part of the complex was estimated to be about 500,000, corresponding to the total apo B in an LDL molecule. This result was confirmed by chemical cross-linking of apo B in Tween 80. Under an electron microscope the apo B-Tween 80 complex appeared as a flexible string, a little less than 1,000 A in length and 50 to 60 A in width.

Apolipoproteins↗
PubMed1980

A cross-linking study of apo-low density lipoprotein.

Chemical cross-linking with dimethylsuberimidate was applied to the study of apo B interactions in human serum low density lipoprotein (LDL). Since apo B is known to have a mass of 500,000 to 600,000 daltons in non-ionic detergent solutions (i.e., a dimer of apo B based on the molecular weight of 260,000 for a single peptide of apo B), the possibility was investigated that the cross-linking reagent might be used to identify the interacting site of apo B in LDL. Although extensive cross-linking was observed in our experiment most of the reaction took place not between apo B's in one LDL (intramolecular) but between apo B's of different LDL's (intermolecular). Only a small fraction of cross-linked apo B dimer was formed intramolecularly. We interpret the results as indicating that the exposed or hydrophilic regions of LDL are scattered on the surface of LDL and that the protein-protein interaction site is not accessible to dimethylsuberimidate, probably being hidden under the surface layer of LDL.

Apolipoproteins↗
PubMed1980

Thermostability and aliphatic index of globular proteins.

A statistical analysis shows that the aliphatic index, which is defined as the relative volume of a protein occupied by aliphatic side chains (alanine, valine, isoleucine, and leucine), of proteins of thermophilic bacteria is significantly higher than that of ordinary proteins. The index may be regarded as a positive factor for the increase of thermostability of globular proteins.

Alanine↗
PubMed1979

Orientation of the rhodopsin sugar moiety in bovine disk membrane.

Rhodopsin from the bovine rod outer segment contains a covalently linked carbohydrate moiety (Heller, J. & Lawrence, M.A. (1973) Biochemistry 9, 864--868). We studied the location of this carbohydrate moiety on the disk membrane by using ferritin-conjugated concanavalin A and concanavalin A labelled with fluorescein isothiocyanate. Electron microscopic observation of sonicated disk membrane that was labelled with ferritin-concanavalin A revealed the electron-dense image of ferritin on the inner surface of the disk membrane and not on its outer surface. Intact disk membrane that was similarly treated with ferritin-concanavalin A showed a complete absence of ferritin molecules on its surface. In an independent series of experiments we confirmed that the sonicated disk membrane bound three to five times more fluorescein-labelled concanavalin A than the intact disk membrane did. From these experiments we conclude that the carbohydrate moiety of bovine rhodopsin is located on the inner surface of the disk membrane, in agreement with the report by Rohlich on the frog rod outer segment disk membrane (Rohlich, P. (1976) Nature 263, 789--791).

Animals↗
PubMed1978

Dimeric nature of apo-low density lipoprotein extracted with Triton X-100.

Human low density lipoprotein (LDL) was dissolved in 0.3 to 2.0% Triton X-100 at pH 7.5 and apo-LDL (B protein) was extracted from LDL to form B protein-Triton complex. Sedimentation equilibrium study of this complex in a solvent nearly isopycnic to Triton X-100 showed that the molecular weight of the protein in the complex was 570,000. The complex eluted almost at the void volume of a Sepharose 6B column, as would be expected for a complex with a total molecular weight of roughly 900,000, on the assumption that 0.52 g of Triton was bound to 1 g of protein (Helenius, A. and Simons, K. (1972) J. Biol. Chem. 247, 3656-3661). The sedimentation coefficient of the complex gave f/fmin = 2.2, indicating that the complex was either as asymmetric as a fibrinogen molecule or not compact. These results show that B protein exists in its complex with Triton X-100 as an elongated or a loosely expanded dimer based on the molecular weight of monomeric B protein of 270,000. B protein may also exist in LDL as a dimer.

Apolipoproteins↗