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Biomedical subjects

A Ikai

Publications and source records attributed to A Ikai.

18 recordsLinked to original sources
PubMed1992

The active site titration of proteinases by using alpha 2-macroglobulin and high-performance liquid chromatography.

The active site titration for various proteinases relies on the development of optimal enzyme titrants for each proteinase, but these titrants are only available for a limited number of proteinases. We have described a new active site titration method applicable to various kinds of endoproteinases using small quantities of the enzymes. This method was carried out by using alpha 2-macroglobulin (alpha 2M) as a titrant and a high-performance liquid chromatography (HPLC) system. When the proteinase solution was treated with alpha 2M, the active proteinase was trapped by alpha 2M. In this reaction alpha 2M does not usually complex with inactive proteinase. After the reaction of proteinase with an excess of alpha 2M, the reaction mixture is applied to an HPLC gel column to separate the uncomplexed enzyme from the one complexed with alpha 2M. The active proteinase is complexed and eluted with alpha 2M, but the inactive proteinase is eluted at the original elution volume. The same amount of the enzyme was also applied to the column. From the decrease of the peak height at the elution position of the uncomplexed proteinase, we can estimate the ratio between enzymatically active proteinases and total proteinases. To test the usefulness of this method, we applied this method to chymotrypsin and trypsin whose activities were predetermined by conventional active site titration, and there was good agreement between both results. With this new method, we can estimate a proteinase activity with as little as 200 ng of the enzyme, a very small amount compared with those required in conventional methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1992

Protein images obtained by STM, AFM and TEM.

Scanning tunnelling microscopy and atomic force microscopy, one scanning the tunnelling current and the other the repulsive atomic force between same and probe, can give high-quality surface topographies of proteins, which have been difficult to obtain by more conventional methods such as transmission electron microscopy.

Macromolecular Substances↗
PubMed1992

Bandeiraea simplicifolia lectin I and Vicia villosa agglutinin bind specifically to the vomeronasal axons in the accessory olfactory bulb of the rat.

The binding of 21 lectins to the accessory olfactory bulb (AOB) of the rat was examined by histochemistry. Two lectins [Bandeiraea simplicifolia lectin I (BSL-I) and Vicia villosa agglutinin (VVA)] bound specifically to the vomeronasal (VN) axons in the AOB. Seven lectins (Datura stramonium lectin, Erythrina cristagalli lectin, Lycoperisicon esculentum lectin, Ricinus communis agglutinin I, soybean agglutinin, Solanum tuberosum lectin, and Ulex europaeus agglutinin) bound to both VN axons in AOB and olfactory axons in the main olfactory bulb. BSL-I and VVA are useful as the marker of VN axons. This selective binding of lectins indicates the presence of specific glycoconjugates on the surface of VN axons.

Animals↗
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↗
PubMed1977

Proteolysis of apoproteins in human serum low density lipoprotein.

Proteolytic treatment of human serum low density lipoprotein (LDL) resulted in the observation of interesting time-dependent changes in the sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern of apo-LDL. Five major fragments with well-defined relative mobilities appeared within 30 min of protease treatment. Prolonged treatment with subtilisin caused changes in the amount of peptides in each of the five bands but their positions on the gel remained unchanged. Periodic acid-Schiff base staining of the gel showed a proteolytic fragment with an apparent molecular weight of 110.000 (actually a cross-linked dimer of two peptides with molecular weights of 77,000 and 68,000) to be a carbohydrate-bearing peptide that was most resistant to further proteolysis and therefore responsible for the interaction between the digested LDL and concanavalin A.

Apolipoproteins↗
PubMed1977

Properties of opsin-lipid complex in aqueous 2-chloroethanol.

Cattle and squid opsins were found to be associated with phospholipids after extensive dialysis of the salt-free digitonin extract of rhodopsin against 30% aqueous 2-chloroethanol (v/v) at pH 2.5. The approximates sizes of opsin-lipid complexes were estimated by sedimentation studies to be around 110,000 and 150,000 daltons, respectively, for the cattle and the squid opsin. Phospholipids did not dissociate from opsin even in 80% 2-chloroethanol. The complexes were purified by passage through a Sephadex G-200 gel column equilibrated with 30% 2-chloroethanol. The optical properties of the complex suggested the presence of beta-conformation and a small amount of alpha-helix in solubilized cattle opsin.

Animals↗
PubMed1976

Denaturation of subtilisin BPN' and its derivatives in aqueous guanidine hydrochloride solutions.

The denaturation of subtilisin BPN' (EC 3.4.21.14) in guanidine hydrochloride was studied in order to find possible reasons for the exceptional stability of this enzyme against the action of denaturing agents including guanidine hydrochloride. Chemically modified subtilisins, i.e., phenylmethanesulfonylsubtilisin and thio-subtilisin, were completely denatured in 2 M guanidine hydrochloride at pH 7 without autolysis but they were stable in 0.5 M guanidine hydrochloride for at least 60 h. On the other hand, once completely denatured, the subtilisins remained inactive and in highly unfolded conformations for 60 h or longer after transfer into 0.5 M guanidine solution at pH 7 or 9. No enzymatic activity was regained when the guanidine concentration was lowered to almost zero. We concluded from these and other results described in this paper that this enzyme was thermodynamically unstable in 2 M guanidine hydrochloride at 20 degrees C and at pH 7. We wish to point out the possibility that the denaturation of this enzyme could indeed be irreversible.

Guanidines↗
PubMed1976

Anomalous fluorescence of yeast 3-phosphoglucerate kinase.

The 3-phosphoglycerate kinase (EC 2.7.2.3) of yeast which contains two tryptophyl and eight tyrosyl residues per molecule, displayed an unusualy fluorescence emission spectrum with a maximum at 308 nm when excited at 280 nm. The emission peak shifted to 329 nm when excited at 295 nm. We could confirm that it was due to the efficient quenching of tryptophyl fluorescence as well as to the incomplete energy transfer from tyrosyl to tryptophyl residues. The average fluorescence quantum yield of this protein was 0.076 (excitation at 280 nm) and that of tryptophyl residues was 0.046 (excitation at 295 nm). As the pH of the solution was lowered, the fluorescence intensity of phosphoglycerate kinase at 329 nm dramatically increased between pH 5 and 4, while the position of the peak remained unchanged. When denatured in 4 M guanidine hydrochloride, the protein showed two emission peaks, one at 343 nm and the other at 303 nm.

Binding Sites↗
PubMed1976

Stepwise degradation of serum low denisty lipoprotein by sodium dodecyl sulfate.

The structure of human serum low density lipoprotein (LDL) was investigated by perturbing the LDL structure with sodium dodecyl sulfate (SDS). The change in LDL structure induced by the addition of SDS was monitored by sedimentation velocity measurements, ultraviolet difference spectroscopy, fluorescence spectroscopy and proteolytic digestion of apo-LDL with subtilisin BPN' [EC 3.4.21.14]. As the concentration of SDS was increased from 0.1 mg/ml to 3 mg/ml with LDL concentrations between 2.0 mg/ml and 4.4 mg/ml, the sedimentation coefficient of LDL changed in three distinct steps. It was found by chemical analyses that not more than 30% of the total lipid was lost from LDL in the second step, whereas the final step in the change of sedimentation coefficient corresponded to the complete removal of apo-LDL from the constituent lipids of LDL. The ultraviolet difference spectrum between the native and SDS-treated LDL and the quenching of LDL fluorescence underwent about 80% of the total change while the SDS concentration was only sufficient to cause the second of the three step changes in sedimentation coefficient. SDS-polyacrylamide gel electrophoresis of apo-LDL treated with subtilisin BPN' also showed that more than 70% of apo-LDL became susceptible to proteolysis under the same conditions. These results were interpreted as indicating that the solubilization of 20 to 30% of the lipids on the surface of LDL exposed nearly 80% or more of apo-LDL to the solvent. A small portion of apo-LDL was, however, still firmly anchored to the remaining lipid micelle as long as the concentration of SDS was less than that required to cause the final step of the change in sedimentation coefficient.

Animals↗
PubMed1975

Denaturation and proteolytic digestion of porcine low-density lipoprotein in aqueous guanidine hydrochloride solutions.

The denaturation of porcine low-density lipoprotein (LDL) in aqueous guanidine hydrochloride (GuHCl) was studied by flotation velocity experiments, optical rotatory dispersion and fluorescence spectroscopy. The denaturation of LDL occurred between 2 and 4M GuGCl, where small sigmoidal changes in iptical rotation and fluorescence intensity were noted. The hydrated density of the native LDL was 1.036g/cm-3 and this remained constant upon denaturation in 4M GuHCl. The slope of the flotation coefficient-solvent density curve was 35 per cent less for denatured LDL than for the native LDL. Since there is no indication of splitting of LDL in 4M GuHCl, it is natural to interpret the result in terms of an increase of the translational frictional coefficient by 50 per cent. The observed changes in optical rotation, fluorescence intensity and flotation coefficient in 4M GuHCl were readily reversed and native LDL was recovered after removal of GuHCl by dialysis. Proteolytic treatment of denatured LDL produced digested LDL which had a hydrated density of 1.021g/cm-3 corresponding to the loss of 30 per cent of apo-LDL. The digested LDL behaved like a compact, globular particle in aqueous NaCl solution and in 4M GuHCl. These results can best be interpreted by a model of the LDL particle in which approximately 30 per cent of apo-LDL is exposed to the solvent, such that it can be reversibly denatured by GuHCl and at the same time is easily avalable to proteolytic enzymes, whereas the rest of apo-LDL is tightly associated with lipids and possibly buried inside the lipid moiety. SDS-polyacrylamide gel electrophoresis of the digested LDL revealed four major peptide fragments with sizes ranging from 70,000 to 100,000 daltons. We believe that the method and results described in this paper will have meaningful applications in the study of membrane proteins.

Animals↗