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L Yu

Publications and source records attributed to L Yu.

At least 811 records · Page 45Linked to original sources
PubMed1980

Resolution and reconstitution of succinate-cytochrome c reductase: preparations and properties of high purity succinate dehydrogenase and ubiquinol-cytochrome c reductase.

An improved method was developed to sequentially fractionate succinate-cytochrome c reductase into three reconstitutive active enzyme systems with good yield: pure succinate dehydrogenase, ubiquinone-binding protein fraction and a highly purified ubiquinol-cytochrome c reductase (cytochrome b-c1 III complex). An extensively dialyzed succinate-cytochrome c reductase was first separated into a succinae dehydrogenase fraction and the cytochrome b-c1 complex by alkali treatment. The resulting succinate dehydrogenase fraction was further purified to homogeneity by the treatment of butanol, calcium phosphate gel adsorption and ammonium sulfate fractionation under anaerobic condition in the presence of succinate and dithiothreitol. The cytochrome b-c1 complex was separated into chtochrome b-c1 III complex and ubiquinone-binding protein fractions by careful ammonium acetate fractionation in the presence of deoxycholate. The purified succinate dehydrogenase contained only two polypeptides with molecular weights of 70 000 anbd 27 000 as revealed by the sodium dodecyl sulfate polyacrylamide gel electrophoretic pattern. The enzyme has the reconstitutive activity and a low Km ferricyanide reductase activity of 85 mumol succinate oxidized per min per mg protein at 38 degrees C. Chemical composition analysis of cytochrome b-c1 III complex showed that the preparation was completely free of contamination of succinate dehydrogenase and ubiquinone-binding protein and was 30% more pure than the available preparation. When these three components were mixed in a proper ratio, a thenoyltrifluoroacetone- and antimycin A-sensitive succinate-cytochrome c reductase was reconstituted.

Cytochrome Reductases↗
PubMed1979

Amino acid sequence of subunit V of bovine heart cytochrome oxidase, the heme alpha-containing subunit.

The complete amino acid sequence of the heme alpha-containing subunit V of bovine heart cytochrome oxidase was determined to be: H2N-Ser-His-Gly-Ser-His-Glu-Thr-Asp-Glu-Glu-Phe-Asp-Ala-Arg-Trp-Val-Thr-Tyr-Phe-Asn-Lys-Pro-Asp-Ile-Asp-Ala-Trp-Glu-Leu-Arg-Lys-Gly-Met-Asn-Thr-Leu-Val-Gly-Tyr-Asp-Leu-Val-Pro-Glu-Pro-Lys-Ile-Ile-Asp-Ala-Ala-Leu-Arg-Ala-Cys-Arg-Arg-Leu-Asn-Asp-Phe-Ala-Ser-Ala-Val-Arg-Ile-Leu-Glu-Val-Val-Lys-Asp-Lys-Ala-Gly-Pro-His-Lys-Glu-Ile-Tyr-Pro-Tyr-Val-Ile-Gln-Glu-Leu-Arg-Pro-Thr-Leu-Asn-Glu-Leu-Gly-Ile-Ser-Thr-Pro-Glu-Glu-Leu-Gly-Leu-Asp-Lys-Val-COOH. The subunit V is a single polypeptide which consists of 109 amino acid residues. The protein contains 48.6% hydrophobic residues and 34.0% hydrophilic residues and it is an acidic protein having a net charge of -3 at neutral pH. The molecular weight of subunit V was calculated to be 12,436 and that for the heme alpha-containing polypeptide was 13,295.

Amino Acid Sequence↗
PubMed1979

Biochemical parameters of normal rabbit serum.

An attempt was made to establish the normal range of 27 different parameters in the serum of 45 healthy, purebred, New Zealand White rabbits (3-5 kg). The reproducibility of the results was acceptable. Sensitive isoenzyme patterns (LDH, CK) could change, however, significantly if different methods were used in the bleeding procedure. Isoenzyme patterns (LDH and CK) of rabbit sera were different from that of human sera. All obtained results were compared with earlier data sporadically published in literature on rabbits.

Animals↗
PubMed1978

Rapid determination of quinidine in human plasma by high-performance liquid chromatography.

A sensitive and specific method for the determination of quinidine in plasma is described. Quinidine is extracted with chloroform, the extract is evaporated and reconstituted with methanol and the methanol extract is analyzed by high-performance liquid chromatography using a silica gel column. The recovery of quinidine from plasma varied between 93.0 to 100%. Quinidine levels as low as 12 ng/ml can be detected by this method.

Chromatography, Gas↗
PubMed1978

The indispensability of phospholipid and ubiquinone in mitochondrial electron transfer from succinate to cytochrome c.

The indispensability of phospholipid and ubiquinone (Q) in mitochondrial electron transfer was studied by depleting phospholipid and Q in succinate-cytochrome c reductase and then replenishing the depleted enzyme. More than 90% of phospholipid and Q was removed by repeated ammonium sulfate-cholate fractionation. The depleted succinate-cytochrome c reductase showed no enzymatic activity for succinate leads to c or QH2 leads to c and yet retained most of the succinate leads to Q activity. All enzymatic activity was restored upon the addition of Q and phospholipid. Restoration required the addition of Q prior to the addition of phospholipid. Reversing the addition sequence or addition of a mixture of phospholipid and Q resulted only in a small restoration of activities. The conditions for restoration are given in detail. Removal of phospholipid from succinate-cytochrome c reductase resulted in reduction of cytochrome c1 in the absence of exogenous electron donor. Replenishing the preparation with phospholipid brought about the reoxidation of cytochrome c1 in the absence of electron acceptor or oxygen.

Animals↗
PubMed1977

Subunit structure of the reconstitutively active cytochrome b-c1 complex. Determination of amino acids and molar distribution of subunit fractions from gel electrophoresis.

A quantitative method has been developed to analyze the amino acid composition of protein subunits directly from the Coomassie Blue-stained band of polyacrylamide gel columns after electrophoresis. It is an improved method originally reported by Houston (Houston, L. L. (1971) Anal. Biochem. 44, 81--88). The results obtained can be thus used for the calculation of the molar ratios of subunit components of protein. The manipulation of the method and computation of the results are illustrated by a very complicated lipoprotein complex. The subunit molar ratios of the reconstitutively active cytochrome b-c1 complex were determined to be 2, 2, 2, 3, 2, 2, and 5 among the seven bands of the corresponding molecular weights of 53 000, 50 000, 37 000, 30 000, 28 000, 17 000, and 15 000, from gel electrophoretic columns. The amino acid composition of each subunit fraction determined directly from hydrolysis of gel was comparable with that obtained by actual isolation of each subunit.

Amino Acids↗
PubMed1977

Identification of subunits of bovine heart cytochrome oxidase.

Purified lipid-depleted cytochrome oxidase, at purity of 12--14 nmol heme a per mg protein, has been shown to contain seven non-identical subunits in the ratio of unity. Their molucular weights on polyacrylamide gel are, in thousands, 40, 21, 14.8, 13.5, 11.6, 9.5, and 7.6 from gel electrophoresis after dissociation in sodium dodecyl sulfate and beta-mercaptoethanol. The molar ratio is determined by the amino acid composition of each subunit obtained from direct hydrolysis of the stained polyacrylamide gel slices. The amino acid composition of the isolated subunits I and II determined by regular hydrolysis method is found practically the same as that from direct hydrolysis of gel slices. The heme-associated polypeptides are identified with subunits of molecular weights of 40.10(3) and 11.6.10(3). One of the two coppers associated with the polypeptide of molecular weight of 21 000. The second copper may be associated with heme in the subunit of 40.10(3). Evidence of the existence of interpolypeptide disulfide linkages is presented.

Amino Acids↗