Biomedical subjects

J Ozols

Publications and source records attributed to J Ozols.

At least 55 records · Page 3Linked to original sources

PubMed1988

Isolation and characterization of human platelet glycoprotein IX.

Human platelet glycoprotein IX is a small (Mr 17,000) surface glycoprotein present in the plasma membrane as a 1:1 non-covalent complex with glycoprotein Ib (Mr 165,000). Glycoprotein IX was purified to near homogeneity by sequential wheat germ agglutinin and immuno-affinity chromatography, followed by gel filtration chromatography under denaturing conditions. Purified glycoprotein IX was characterized by determination of its amino acid composition and its NH2-terminal amino acid sequence (thr-lys-asp-xxx-pro-ser-xxx-leu-thr-(thr)2-arg-ala-(leu)-(glu)-xxx-met- gly), and monospecific anti-glycoprotein IX antibody was prepared. The study outlines a useful approach for separating and characterizing glycoprotein IX, free from other members of the glycoprotein Ib complex.

Amino Acid Sequence↗

PubMed1988

Complete covalent structure of 60-kDa esterase isolated from 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rabbit liver microsomes.

The 60-kDa esterase was isolated from liver microsomes of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rabbits and its complete amino acid sequence determined. Automated sequence analysis of intact protein, as well as characterization of the peptides obtained from enzymatic and chemical cleavages, led to the elucidation of the primary structure. The protein is a single polypeptide consisting of 539 residues and molecular weight 59,478. The active site serine is 195, and another diisopropylphospho binding site is at histidyl 441. Carbohydrate chains are attached at aspariginyl residues 61 and 363. Although 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment induces this esterase severalfold, the amino acid sequence of the induced enzyme is identical to that of the enzyme isolated from liver microsomes of untreated rabbits. The sequence of the microsomal esterase is 30% identical with the sequences of human serum cholinesterase and the acetylcholinesterase from Torpedo californica. There is also a close homology between the 60-kDa esterase and the COOH-terminal domain of bovine thyroglobulin.

Acetylcholinesterase↗

PubMed1988

Bacterial synthesis of active rat stearyl-CoA desaturase lacking the 26-residue amino-terminal amino acid sequence.

Two clones containing inserts in pBR322 that together include the entire 1074-base open reading frame coding for the 358 amino acids of rat liver stearyl-CoA desaturase have been used to construct expression vectors for residues 3-358 and 27-358 fused to the first 6 residues of beta-galactosidase and several amino acids of the multiple cloning site of pUC8. Growth of transformed Escherichia coli under conditions for suppression of the lac promoter, followed by subsequent induction of these cultures results in the synthesis of higher levels of desaturase proteins than those found in induced rat liver. The proteins are almost completely associated with the membrane fraction of cell homogenates. Posttranslational iron insertion into the apoproteins, either in vitro with membrane preparations or by iron addition during induction, results in the formation of active holoenzyme which can be reconstituted with NADH cytochrome b5 reductase and cytochrome b5 to form an active stearyl-CoA desaturase system. The deletion of the first 26 amino-terminal amino acid residues does not affect either enzyme activity or membrane binding. Therefore, the unusual sequence of 11 residues containing 10 amino acids with hydroxyl groups plays no apparent significant role in either protein insertion into membranes or iron chelation. Since the protein product for residues 3-358 is processed even further to delete the initial 33 amino-terminal residues, the limiting polypeptide primary structure required for an active membrane-bound catalyst is even smaller than this initial deletion mutation indicates.

Amino Acid Sequence↗

PubMed1987

Isolation and characterization of a 60-kilodalton glycoprotein esterase from liver microsomal membranes.

A glycoprotein having a subunit weight of approximately 60,000 was isolated from rabbit liver microsomes. It is a predominant component of the hepatic microsomal membrane and reacts rapidly with diisopropylphosphorofluoridate (DFP), resulting in the loss of enzymatic activity toward artificial substrates such as acyl esters of o-nitrophenols. Automated Edman degradation of this protein together with sequence analysis of peptides provided the NH2-terminal sequence of some 70 residues as follows: His-Pro-Ser- Ala-Pro-Pro-Val-Val-Asp-Thr-Val-Lys-Gly-Lys-Val- Leu-Gly-Lys-Phe-Val-Ser-Leu-Glu-Gly-Phe-Ala-Gln- Pro-Val-Ala-Val-Phe-Leu-Gly-Val-Pro-Phe-Ala-Lys- Pro-Pro-Leu-Gly-Ser-Leu-Arg-Phe-Ala-Pro-Pro-Gln- Pro-Ala-Glu-Ser-Trp-Ser-His-Val-Lys-Asn (CHO)- Thr-Thr-Ser-Tyr-Pro-Pro-Met-Cys-Ser-Ser. A carbohydrate attachment was identified at asparaginyl residue 61. The COOH-terminal peptide of the protein was isolated from two independent enzymatic digests, and its sequence was established as Arg-Glu-Thr-Glu-His-Ile-Glu-Leu. In order to isolate the DFP binding peptide, liver microsomes were labeled with [3H]DFP and the 60-kDa protein containing covalently bound DFP isolated in pure form. Following reduction and carboxymethylation, the DFP-labeled protein was fragmented with trypsin and the digest subjected to gel filtration. Digestion of the labeled peptide preparations with chymotrypsin followed by chromatography of the digest yielded two diisopropylphosphoryl (DIP) peptides. Automated Edman degradation of these peptides provided the following amino acid sequences: Gly-Glu-DIPSer- Ala-Gly-Gly-Gln-Ser-Val-Ser-Ile-Leu-Leu-Leu-Ser- Pro and Thr-Val-Ile-Gly-Asp-DIPHis-Gly-Asp-Glu-Ile-Phe. The active site serine peptide of the 60-kDa protein shows some 70% similarity to the active center region of choline esterases. While the postulated active histidyl residue in choline esterases has not been identified, it is proposed that the DFP binding histidine of the 60-kDa protein corresponds to His-438/440 of choline esterases.

Amino Acid Sequence↗

PubMed1987

Isolation and characterization of the alpha and beta chains of human platelet glycoprotein Ib.

Human platelet glycoprotein Ib has been purified in milligram amounts from platelets obtained by pheresis of thrombocytotic donors. Purification steps included lectin (wheat germ agglutinin) and immuno (murine monoclonal anti-glycoprotein Ib antibody)-affinity chromatography. The disulfide-linked individual alpha and beta chains of GPIb were separated and the amino-terminal amino acid sequence of each chain was determined. Rabbit polyclonal antibody directed against each individual chain was prepared by affinity chromatography and shown to be monospecific by western blot analysis using whole platelet lysate as antigen. These studies outline a useful approach to isolate and characterize the individual chains of GPIb.

Amino Acid Sequence↗

PubMed1987

Isolation and characterization of the receptor on human neutrophils that mediates cellular adherence.

The receptor on human neutrophils (polymorphonuclear leukocytes or PMN) that mediates cellular adherence has been purified from the peripheral blood PMN obtained from an individual with chronic myelogenous leukemia (CML). This receptor consists of two noncovalently associated subunits, designated alpha M (Mac-1 alpha, CD11b) (Mr = 170,000) and beta (Mac-1 beta, CDw18) (Mr = 100,000), respectively, which are identical on normal and CML PMN. The subunits were purified by monoclonal antibody 60.1-Sepharose (anti-alpha M) affinity chromatography and separated in 5-nmol quantities by high pressure liquid chromatography on a TSK-4000 gel filtration column. Subunits were characterized by amino acid composition, NH2-terminal amino acid sequence, and carbohydrate content. The NH2-terminal sequence of the human PMN alpha M subunit contains regions of homology with the human platelet glycoprotein IIb alpha. We conclude that nanomole amounts of individual alpha M and beta subunits of the receptor on human PMN that mediates cellular adherence can be isolated and separated using CML PMN.

Amino Acids↗

PubMed1986

Construction and sequence of cDNA for rat liver stearyl coenzyme A desaturase.

Hepatic poly(A+) RNA from rats induced for stearyl-CoA desaturase was used for primer-extension of cDNA coding for stearyl-CoA desaturase. Previously, Northern blot analysis showed that translatable desaturase mRNA is 4,900 nucleotides in length (Thiede, M. A., and Strittmatter, P. (1985) J. Biol. Chem. 260, 14459-14463). Six overlapping cDNAs, ranging from 850 to 1450 bases, were used to compile the 4,689-nucleotide sequence. The cDNA includes a 1,074-base open reading frame coding for 358 amino acids, corresponding to a molecular mass of 41,400 daltons. Positive identification of this open reading frame was accomplished by matching the amino acid sequence of both amino-terminal and cyanogen bromide peptides of the purified enzyme with regions of the sequence deduced from the cDNA. Amino acid composition data from the cDNA compares well with that from the desaturase. The protein contains 62% hydrophobic amino acids. An interesting feature of this mRNA is the 3,500-base 3' noncoding region, which has been localized on a single 3' exon by Southern blot analysis.

Amino Acid Sequence↗

PubMed1986

Identification of the essential cysteine residue of NADH-cytochrome b5 reductase.

The soluble catalytic domain of NADH-cytochrome b5 reductase was radiolabeled with [14C]N-ethylmaleimide. Reaction for a limited time resulted in incorporation of 0.41 eq of N-ethylmaleimide and loss of 36% of the enzyme activity. Chromatography on a 5'-ADP affinity column separated the reductase which was modified with N-ethylmaleimide from the unreacted enzyme; the isolated derivative constituted 37% of the total material, was completely inactivated, and contained 1.00 eq of N-ethylmaleimide. Cyanogen bromide cleavage of the derivative demonstrated that radioactivity was limited to a single peptide which contained both Cys-283 and Cys-297. Tryptic hydrolysis of this cyanogen bromide peptide showed that the radioactivity was associated with Cys-283. Automated sequenator analysis confirmed that Cys-283 was the radiolabeled residue. These data demonstrate unambiguously that Cys-283 provides the essential thiol group of cytochrome b5 reductase.

Amino Acids↗

PubMed1986

Complete amino acid sequence of a cytochrome P-450 isolated from beta-naphthoflavone-induced rabbit liver microsomes. Comparison with phenobarbital-induced and constitutive isozymes and identification of invariant residues.

The complete covalent structure of a cytochrome P-450, form 4, isolated from liver microsomes of beta-naphthoflavone-induced rabbits was determined. The S-carboxyamidomethylated protein was cleaved with cyanogen bromide, endoproteinase Lys-C, and trypsin before and after succinylation. Selected peptides from CNBr digests of alkylated rabbit cytochrome P-450 forms 3a and 3c were also isolated and sequenced. Form 4 exhibited microheterogeneity due to the presence of several truncated forms. The existence of multiple NH2-terminal residues for form 4 was confirmed by the isolation and sequence analysis of the corresponding tryptic peptides. The predominant form contained 514 residues, corresponding to Mr 58,030. A peptide having Gly-232 and Gln-246 replaced by Ser and Asn residues, respectively, was also found in the isozyme preparation investigated here. The amino acid sequences of form 4 and selected peptide sequences from forms 3a and 3c were compared with the primary structures of forms 2 and 3b (previously determined in this laboratory). This comparison identified some 90 invariant residues. A cysteinyl residue at position 456, earlier reported as the heme-binding cysteine 436 (Heineman, F. S., and Ozols, J. (1982) J. Biol. Chem. 257, 14988-14999), was also present in forms 4, 3a, and 3c. Other single invariant residues identified were form 4/forms 2,3b, Trp-132/121, and His 270/252. The tyrosyl residues at positions 71/62 and 365/348 were also invariant. The latter is present in the "conserved segment" of the protein, residues 363/346 to 375/359, and may be involved in the substrate binding of cytochrome P-450. Also a lysyl residue, formerly identified by other laboratories to be involved in the electron transfer between the reductase and cytochrome P-450 form 2, was invariant in all five species. This lysyl residue corresponds to Lys-402 in form 4 or Lys-384 in the other forms.

Amino Acid Sequence↗

PubMed1985

Complete amino acid sequence of steer liver microsomal NADH-cytochrome b5 reductase.

The complete covalent structure of liver microsomal NADH-cytochrome b5 reductase from steer liver microsomes was determined. Cleavage at methionyl bonds gave 10 peptides accounting for all the residues of the protein. Acid cleavage of the reductase at the Asp-Pro bonds gave three peptides accounting for all the CNBr peptides in the molecule. Subfragmentation of these peptides by chemical and enzymatic cleavage provided overlaps which established all the fragments in an unambiguous sequence of 300 residues, corresponding to Mr 34,110. Limited tryptic digestion cleaved reductase at residues 28 and 119, yielding a preparation having two noncovalently linked peptides having a conformation which binds flavin and retains the structural features essential for NADH-cytochrome b5 activity. A model for the secondary structure of cytochrome b5 reductase is proposed that is based on computer-assisted analysis of the amino acid sequence. In this model the beta-turns are predominant and there is some 25% alpha and 30% beta structure.

Amino Acid Sequence↗

PubMed1985

The complete amino acid sequence of a constitutive form of liver microsomal cytochrome P-450.

The complete covalent structure of the constitutive cytochrome P-450, form 3b, from rabbit liver microsomes was determined. The apocytochrome contains 490 amino acid residues in a single polypeptide chain, Mr = 55,860. Peptides from selective chemical and proteolytic cleavages were isolated by a combination of gel filtration and high performance liquid chromatography and sequenced by automated Edman degradation. Overlapping peptide sequences were used to deduce the complete sequence. The constitutive form is only 46% homologous to the phenobarbital-induced cytochrome P-450 (Heinemann, F. S., and Ozols, J. (1983) J. Biol. Chem. 258, 4195-4201) and contains a deletion at position 22. Strongly conserved regions include Cys435 and a previously identified tryptic peptide, residues 345-357. The distribution of hydrophobic segments is used to predict the membrane topology of the protein, and four possible orientations of this protein in the membrane are presented.

Amino Acid Sequence↗

PubMed1984

Identification of the NH2-terminal blocking group of NADH-cytochrome b5 reductase as myristic acid and the complete amino acid sequence of the membrane-binding domain.

The NH2-terminal blocking group of the membrane-binding domain of NADH-cytochrome b5 reductase has been deduced as myristic (n-tetradecanoyl) acid. This fatty acid was identified by gas chromatography of the digest of the NH2-terminal tetrapeptide of cytochrome b5 reductase. Fast atom bombardment and direct chemical ionization mass spectroscopy of the underivatized NH2-terminal tetrapeptide confirmed the presence of myristic acid, identified its linkage to the NH2 terminus and established CH3(CH2)12-CO-Gly-Ala-Gln-Leu as the NH2-terminal sequence. In addition, the complete amino acid sequence of the membrane-binding domain of cytochrome b5 reductase is also reported. The finding of a myristic acyl chain on the NH2-terminal segment, comprised of hydrophobic amino acid residues, implies that the function of the myristate group may be other than simply to anchor the reductase to the microsomal membrane. This post-translational modification, presumably in the endoplasmic reticulum, may selectively stabilize a particular membrane structure and orientation that optimally facilitates electron transport on the cytosolic surface of this membrane organelle.

Amino Acid Sequence↗

PubMed1984

The covalent structure of hepatic microsomal epoxide hydrolase. I. Isolation and characterization of the cyanogen bromide fragments.

Microsomal epoxide hydrolase was purified to homogeneity from phenobarbital-induced rabbit liver for the purpose of determining the complete amino acid sequence. All of the expected 11 cyanogen bromide fragments of epoxide hydrolase were isolated by a combination of gel filtration and high pressure liquid chromatography. Each was characterized by its amino acid composition and NH2-terminal amino acid sequence. The complete amino acid sequences of the eight small fragments, from 5-29 residues, were determined.

Amino Acid Sequence↗

PubMed1984

The covalent structure of hepatic microsomal epoxide hydrolase. II. The complete amino acid sequence.

The complete amino acid sequence of hepatic microsomal epoxide hydrolase has been determined. The protein contains 455 amino acid residues in a single polypeptide chain and has Mr = 52,691. Peptides from selective chemical and proteolytic cleavages were isolated by a combination of gel filtration and high performance liquid chromatography and sequenced by automated Edman degradation. Overlapping peptide sequences were used to deduce the complete sequence. This is the first epoxide hydrolase and the third microsomal enzyme for which the complete sequence has been determined.

Amino Acid Sequence↗

PubMed1983

Isolation and partial characterization of the NH2-terminal membrane-binding domain of NADH-cytochrome b5 reductase.

The amphipathic flavoprotein NADH-cytochrome b5 reductase from steer liver was converted into the membrane-binding and soluble catalytic domains by controlled subtilisin proteolysis of vesicle-bound, externally oriented reductase. Amino acid analysis of the single nonpolar peptide which remained associated with the vesicles showed that it has a molecular weight of about 6400-6500 and that 65-66% of the amino acid residues are hydrophobic. Both the intact reductase and the nonpolar peptide were blocked to sequencing. Carboxypeptidase Y digestion of the holoenzyme and of a chymotryptically generated flavopeptide, which had lost membrane-binding capacity, released 1 residue of alanine and 2 residues of phenylalanine, indicating a common carboxyl terminus. Partial sequence analysis of the reductase placed the nonpolar peptide to the NH2-terminal side of the subtilisin-generated flavopeptide domain. Thus, the membrane-binding domain of cytochrome b5 reductase is localized at the NH2-terminus of the whole protein. The nonpolar peptide bound to vesicles contains a single fluorescent tryptophan with an emission maximum characteristic of a hydrophobic environment.

Amino Acid Sequence↗

PubMed1983

Isolation and covalent structure of the aspirin-modified, active-site region of prostaglandin synthetase.

Aspirin (acetylsalicylic acid) inhibits prostaglandin synthesis by acetylating a single internal serine residue of the initial enzyme in the biosynthetic pathway, prostaglandin synthetase. In this study, the region of the enzyme that is modified by aspirin has been isolated, and its amino acid sequence has been determined. Sheep vesicular gland [acetyl-3H]prostaglandin synthetase was purified following treatment with [acetyl-3H]aspirin and digest with pepsin. An acetyl-3H-labeled peptic peptide of approximately 25 residues was isolated by high-pressure liquid chromatography, and its amino acid sequence was determined to be Ile-Glu-Met-Gly-Ala-Pro-Phe-Ser-Leu-Lys-Gly-Leu-Gly-Asn-Pro-Ile-Glu-Ser-Pro-Glu-Tyr. The acetylated serine residue was located at position 8 in this sequence. The current study marks this polypeptide sequence as a region related to an active site of the enzyme.

Amino Acid Sequence↗

PubMed1983

The complete amino acid sequence of rabbit phenobarbital-induced liver microsomal cytochrome P-450.

The complete amino acid sequence of the major phenobarbital-induced cytochrome P-450 (P-450LM2) from rabbit liver microsomes has been determined. The protein contains 489 amino acid residues in a single polypeptide chain and has Mr = 55,464. The sequence was compared with the amino acid sequence of P-450CAM and the nucleotide sequence of cDNA obtained from phenobarbital-induced rat liver cytochrome P-450 mRNA. These comparisons suggest that, despite functional similarities, the structural homology between microbial and microsomal cytochromes P-450 is limited to a single 8-residue region, and, in contrast, the structure of inducible microsomal cytochrome P-450 isozymes is highly conserved among mammalian species. Furthermore, we propose that the thiolate heme ligand of cytochrome P-450 is contributed by a cysteinyl residue near the COOH terminus, position 434 in the rabbit P-450LM2 sequence, based on the homology in this region with P-450CAM. The NH2 terminus of the protein from residues 1-310 is characterized by 8 hydrophobic segments 18-23 residues long, each of which is terminated by a cluster of charged amino acid residues. Residues 320-443 comprise a hydrophilic region which contains the putative heme binding cysteinyl residue as well as segments of homology with a constitutive rabbit cytochrome P-450 isozyme. The sequence data suggest that cytochrome P-450LM2 contains multiple transmembranous segments as well as a hydrophilic cytoplasmic domain. The hydrophilic domain contains regions of homology with several other cytochromes P-450, and thus appears to have an essential role in the biological function of the protein.

Amino Acid Sequence↗

PubMed1982

The covalent structure of rabbit phenobarbital-induced cytochrome P-450. Partial amino acid sequence and order of cyanogen bromide peptides.

The phenobarbital-induced isozyme of cytochrome P-450 was isolated from rabbit liver microsomes and subjected to chemical and proteolytic degradation. The resulting peptides were isolated exclusively by reverse phase high pressure liquid chromatography. Automated sequence analysis was employed to determine the linear arrangement of 385 residues and the order of all CNBr peptides. The NH2 terminus of the cytochrome P-450 consists of five hydrophobic segments 18 to 23 residues long, separated by polar regions of 8 to 15 residues. The COOH terminus contains a hydrophilic region 120 residues long as well as several hydrophobic segments. A tridecapeptide, previously found to be analogous to a tryptic peptide from a constitutive P-450 isozyme (Ozols, J., Heinemann, F. S., and Johnson, E. F. (1981) J. Biol. Chem. 256, 11405-11408) was positioned within the hydrophilic region of the COOH terminus. The amino acid sequence is interpreted in terms of a model for the topology of the cytochrome in the membrane which can be used as a basis for further experiments. Comparison of this sequence with the cytochrome P-450CAM sequence (Haniu, M., Armes, L. G., Tanaka, M., Yasunobo, K. T., Shastry, B. S., Wagner, G. C., and Gunsalus, I. C. (1982) Biochem. Biophys. Res. Commun. 105, 889-894) revealed a single homologous region which contains a cysteinyl residue. The amino acid sequence of his segment is as follows: P-450 microsomal/P-450CAM:Ile/Leu-Cys-Leu-Gly-Gln/Glu-Ser/Gly-Leu/Ile-Ala-Arg. The amino acid sequence data were also compared with the amino acid sequence deduced from the nucleotide sequence of phenobarbital-inducible cytochrome P-450 mRNA from rat liver (Kurijama-Fuji, Y., Mizukami, Y., Kawajiri, K., Sogawa, K., Muramatsu, M. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 2793-2797). This comparison suggests that the structure of the phenobarbital-induced isozyme is highly conserved among mammalian species.

Amino Acid Sequence↗