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Biomedical subjects

J Knudsen

Publications and source records attributed to J Knudsen.

At least 91 records · Page 5Linked to original sources
PubMed1991

Gene synthesis, expression in Escherichia coli, purification and characterization of the recombinant bovine acyl-CoA-binding protein.

A synthetic gene encoding the 86 amino acid residues of mature acyl-CoA-binding protein (ACBP), and the initiating methionine was constructed. The synthetic gene was assembled from eight partially overlapping oligonucleotides. Codon usage and nucleotides surrounding the ATG translation-initiation codon were chosen to allow efficient expression in Escherichia coli as well as in yeast. The synthetic gene was inserted into the expression vector pKK223-3 and expressed in E. coli. In maximally induced cultures, recombinant ACBP constitutes 12-15% of total cellular protein. A fraction highly enriched for recombinant ACBP was obtained by extracting induced E. coli cells with 1 M-acetic acid. Recombinant ACBP was purified to homogeneity by successive use of gel-filtration chromatography, ion-exchange chromatography and reverse-phase h.p.l.c. Recombinant ACBP differed from native ACBP by lacking the N-terminal acetyl group. The acyl-CoA-binding characteristics of recombinant ACBP did not differ from those of native ACBP, and the two proteins showed the same ability to induce medium-chain acyl-CoA synthesis by goat mammary-gland fatty acid synthetase. It was concluded that the N-terminal acetyl group is not important for acyl-CoA binding.

Acyl Coenzyme A↗
PubMed1991

The amino acid sequence of a major protein component in the light harvesting complex of the green photosynthetic bacterium Chlorobium limicola f. thiosulfatophilum.

A 7.5-kDa protein has been isolated from chlorosomes of Chlorobium limicola f. thiosulfatophilum and the complete primary structure determined by a combination of automatic Edman degradation and plasma desorption mass spectrometry. The 74-residue protein shows great homology to a similar protein of unknown function which has been isolated from Pelodictyon luteolum but otherwise no significant homology to other proteins can be found. The possible role of the protein in the structure and function of the chlorosome is discussed.

Amino Acid Sequence↗
PubMed1991

Human papillomavirus type 16 in vulvar carcinoma, vulvar intraepithelial neoplasia, and associated cervical neoplasia.

Vulvar intraepithelial neoplasia (VIN) is becoming more widespread and the patients are becoming still younger. Although progression to invasive vulvar carcinoma is uncommon, local recurrences are frequent and about one-quarter of the patients have multicentric genital disease. The aim of the present study was to search for a possible significant association of human papillomavirus (HPV) infection with vulvar carcinoma, recurrences, and multicentric disease. We used the polymerase chain reaction to examine vulvar and cervical biopsies from 43 patients with vulvar neoplasia for HPV type 16, which is the subtype most often detected in genital malignant or premalignant lesions. HPV 16 DNA sequences were found in 14 of 24 (58%) vulvar squamous carcinomas and in 15 of 19 (79%) VIN lesions. Nine patients (21%) had associated cervical neoplasia and six of these harbored HPV 16 in both lesions. Patients with recurrent intraepithelial neoplasia had a significantly higher incidence of HPV 16-positive lesions. No association was found with regard to the occurrence of multicentric disease or risk of malignant progression.

Adult↗
PubMed1991

Lactating goat mammary gland cells in culture.

1. Isolated mammary gland cells were cultured embedded in collagen gels or as monolayers on floating collagen gels. Under these conditions the cells were able to grow for at least 6 weeks during five passages. Growth was sustained in M199/F12 (1:1) supplemented with insulin, hydrocortisone, epidermal growth factor, tri-iodothyronine, estradiol and bovine serum albumin. 2. The cells secreted lactose into the medium in significant amounts throughout the culture period. 3. Prolactin had a slightly stimulatory effect as had fetal bovine serum on growth and protein synthesis, but none of these factors were obligatory in this respect. Insulin-like growth factor I (Somatomedin C) could replace high concentrations of insulin whereas bovine growth hormone had no detectable effect. 4. Depending on the hormone content of the medium and the age of the culture, different labelling patterns of the arachidonic acid-containing phospholipids were observed. The effect of prolactin on phosphatidyl inositol and arachidonic acid metabolism was studied.

Animals↗
PubMed1991

Acyl-CoA-binding and transport, an alternative function for diazepam binding inhibitor (DBI), which is identical with acyl-CoA-binding protein.

Acyl-CoA binding protein (ACBP) was originally identified as an artifact in a preparation of fatty acid binding protein. The amino acid sequence of ACBP from bovine, rat and human liver is identical to the sequence of diazepam binding inhibitor (DBI) from these species. ACBP and DBI are therefore one and the same protein. The tertiary structure of ACBP in solution has been determined by 2D-NMR. ACBP consists of 4 alpha-helixes, covering the sequence from amino acid 2-11, 20-38, 51-62 and 72-85, respectively. The protein is folded so that it forms a boomerang type of structure with helix 1 and 2 arranged antiparallel in the one arm of the boomerang, helix 3 and the non-helical part between helix 2 and 3 form the second arm in the boomerang. Helix 4 is located in an angle behind helix 1 and 2. NMR measurements of chemical shifts, induced by acyl-CoA binding, indicate that the binding site is located in the bottom of the V formed between the two arms of the boomerang. This location of the binding site is confirmed with affinity labelling with radioactive photoreactive acyl-CoA esters. ACBP does not bind free CoA or free fatty and short chain acyl-CoA esters (C2-C8). The affinity increases with increasing length of the acyl chain from C10-C20 and drops again in acyl-CoA esters with 22 and 24 carbon in the acyl chain.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyl Coenzyme A↗
PubMed1990

Determination by photoaffinity labelling of the hydrophobic part of the binding site for acyl-CoA esters on acyl-CoA-binding protein from bovine liver.

Acyl-CoA esters containing the photoreactive acids 12-(4'-azido-2'-nitrophenoxy)[1-14C]dodecanoic acid ([14C]AND-acid) or N-(4'-azido-2'-nitro-[3'-5'-3H]phenyl)-12-aminododecanoic acid ([3H]NANPA-acid) were synthesized. The photoreactive acyl-CoA esters could be bound to bovine acyl-CoA-binding protein (ACBP) and photocrosslinked to the protein. The photocrosslinked acyl-CoA-ACBP complex was separated from unlabelled ACBP on reverse-phase h.p.l.c. and the purified complex was digested with trypsin, Staphylococcus aureus V8 proteinase or endoproteinase Asp-N. By four independent peptide maps it was shown that the amino acids taking part in forming the hydrophobic binding site for acyl-CoA esters in bovine ACBP are located on the peptide segment from Asp21 to Asp38. Both photoreactive acyl-CoA esters used in this study labelled strongly in the segment from Tyr28 to Ala34. 12-(4'-Azido-2'-nitrophenoxy)[1-14C]-dodecanoyl-CoA ([14C]AND-CoA) also introduced a label at position Asp38, but o labelling was found before Ser29. In contrast, N-(4'-azido-2'-nitro[3',5'-3H]phenyl)-12-aminododecanoyl-CoA [3H]NANPA-CoA) also labelled the segment from Asp21 to Tyr28. The difference in labelling by the two photoreactive ligands is most likely caused by different mobility of the arylazido group when linked to the fatty acid either through a phenolic O- or an anilinic N- bond.

Acyl Coenzyme A↗
PubMed1990

Cardiac fatty acid-binding proteins. Isolation and characterization of the mitochondrial fatty acid-binding protein and its structural relationship with the cytosolic isoforms.

In the course of our studies on the structural diversity of the isoforms of cardiac fatty acid-binding proteins (cFABPs), a cardiac-type FABP from the matrix of bovine heart mitochondria was purified to homogeneity and obtained as a single 15-kDa protein with an isoelectric point of 4.9. The primary structures of this protein and of the two isoforms isolated from the cytosol (pI4.9-cFABP and pI 5.1-cFABP) were investigated by means of plasma desorption mass spectrometry and sequencing of peptides. All three proteins are amino-terminally blocked with an acetyl group and shown to be colinear with the sequence deduced from a cDNA clone for bovine heart fatty acid-binding protein (Billich, S., Wissel, T., Kratzin, H., Hahn, U., Hagenhoff, B., Lezius, A. G., and Spener, F. (1988) Eur. J. Biochem. 175, 549-556) except for the residue at position 98. This residue is demonstrated to be the molecular origin of bovine cFABP isoforms since pI 5.1-cFABP contains Asn98 in accordance with the sequence derived from the cDNA, whereas in pI 4.9-cFABP, this position is occupied by Asp98. Moreover, mitochondrial FABP is identical to pI 4.9-cFABP. Molecular masses of pI 4.9-cFABP (14,679 +/- 10 Da) and pI 5.1-cFABP (14,678 +/- 20 Da) determined by plasma desorption mass spectrometry coincide with that calculated from the cDNA (14,673 Da). Hence, residues linked to these proteins by posttranslational modification are not present, and the Asn-Asp exchange is the sole origin of heterogeneity of mitochondrial and cytosolic fatty acid-binding proteins from bovine heart.

Amino Acid Sequence↗
PubMed1990

Comparison of the binding affinities of acyl-CoA-binding protein and fatty-acid-binding protein for long-chain acyl-CoA esters.

Bovine and rat liver acyl-CoA-binding proteins (ACBP) were found to exhibit a much higher affinity for long-chain acyl-CoA esters than both bovine hepatic and cardiac fatty-acid-binding proteins (hFABP and cFABP respectively). In the Lipidex 1000- as well as the liposome-binding assay, bovine and rat hepatic ACBP effectively bound long-chain acyl-CoA ester, h- and c-FABP were, under identical conditions, unable to bind significant amounts of long-chain acyl-CoA esters. When FABP, ACBP and [1-14C]hexadecanoyl-CoA were mixed, hexadecanoyl-CoA could be shown to be bound to ACBP only. The experimental results give strong evidence that ACBP, and not FABP, is the predominant carrier of acyl-CoA in liver.

Acyl Coenzyme A↗
PubMed1990

Is radical hysterectomy always necessary in early cervical cancer?

A semiquantitative histopathologic grading system was used in combination with flow cytometric measurements of tumor cell DNA content to predict the risk of lymph node metastases in early cervical cancer. A retrospective study of 126 stage IB patients showed that a group with no risk of lymph node involvement could be identified by the use of both the histopathologic score and the DNA index. The results were confirmed in a prospective investigation of 59 new patients. Simple hysterectomy may be advised in low-risk patients.

DNA, Neoplasm↗
PubMed1989

Acyl-CoA-binding protein in the rat. Purification, binding characteristics, tissue concentrations and amino acid sequence.

Acyl-CoA-binding protein (ACBP) was purified from rat liver. The Mr was determined as 9932 +/- 10 by mass spectrometry and calculated as 9937.8 from the sequence. The protein binds acyl-CoA esters (C8-C16) with high affinity, but was unable to bind fatty acids. ACBP was found mainly (86%) in the soluble fraction, and the concentration was highest in liver, 5-6 micrograms/mg of soluble protein. The complete primary structure was determined by a combination of gas-phase Edman degradations and mass spectrometry. Extensive use of 252Cf plasma-desorption mass spectrometry facilitated the identification and verification of peptides. Comparison with the previously determined sequence of bovine acyl-CoA-binding protein revealed a very strong sequence similarity (83%), and all of the differences could be accounted for by single base changes.

Acyl Coenzyme A↗
PubMed1989

At what level of serum total creatine kinase activity can measurement of serum creatine kinase MB isoenzyme activity be omitted in suspected myocardial infarction?

The purpose of this study was to establish a discriminatory limit for serum total creatine kinase activity (CK activity) below which CK isoenzyme fractionation is unnecessary. We looked at 2610 serum samples from 1077 consecutive patients with suspected acute myocardial infraction (AMI). The CK activity was determined according to the Scandinavian recommended method. Isoenzymes of CK were separated by agarose gel electrophoresis, followed by fluorometric scanning. When the threshold for CK activity was 150 U/l, none of the samples had a creatine kinase MB isoenzyme activity (CK-MB activity) equal to or higher than 30 U/l (the diagnostic level), which has been found to differentiate between patients with AMI and those without AMI. Only 14 patients (1.3% of all patients investigated) had CK-MB activity peaks between 10 U/l (detection limit) and 30 U/l. Of these, AMI was only diagnosed in one. We recommend that CK-MB activity should be measured only when CK activity is higher than 150 U/l. This would make about 50% of all CK-MB measurements unnecessary.

Aged↗
PubMed1987

Acyl-CoA-binding protein from cow. Binding characteristics and cellular and tissue distribution.

Using the tyrosine fluorescence quenching as a criterion for acyl-CoA binding, we have shown that acyl-CoA-binding protein (ACBP) binds acyl-CoA esters with a chain length greater than C8 with equal affinity. The binding studies indicated a binding stoichiometry of 1 mol of acyl-CoA/2 mol of ACBP. The protein was found in liver, adipose tissue, intestinal mucosa, kidney, heart, brain, muscles and mammary gland. The highest concentration was found in liver cytosol and the lowest in muscles and mammary gland. ACBP could not be shown to bind non-esterified fatty acids.

Acyl Coenzyme A↗
PubMed1987

Amino acid sequence of acyl-CoA-binding protein from cow liver.

Acyl-CoA-binding protein from bovine liver was purified with the use of reverse-phase h.p.l.c. in the final step. The complete amino acid sequence was determined by using a combination of gas-phase Edman degradation and electron-impact and fast-atom-bombardment mass spectrometry. The sequence was confirmed by determination of the Mr by plasma-desorption time-of-flight mass spectrometry.

Amino Acid Sequence↗
PubMed1987

A novel procedure for the preparation and characterization of catalytically active fatty acid synthetase immobilized on sepharose beads.

A novel procedure for immobilization of enzymatically active fatty acid synthetase is presented. The enzyme is coupled to a Sepharose 4B matrix containing covalently attached antibodies which recognize, and bind specifically to, the thioesterase domain of this polyfunctional enzyme. A continuous flow system is described for assay of the immobilized enzyme. Fatty acid synthetase activity apparently is not limited by movement of substrates through the Nernst diffusion layer surrounding the matrix particles, since normal Michaelis-Menten kinetics are observed and reaction rates are independent of flow rate. The Km values for acetyl-CoA and malonyl-CoA, the pH/activity profile, and the reaction products are essentially the same as for the freely soluble enzyme, although the specific activity is lower by about 55%. The preparation and characterization of immobilized subunits of the enzyme could provide a valuable approach for studying the role of structural and functional subunit interactions in the enzyme. In addition, the immobilized enzyme offers a model for studying the properties of this enzyme in a highly structured environment such as might exist in vivo, permitting study of both physical and functional interactions of fatty acid synthetase with other lipogenic enzymes.

Acetyl Coenzyme A↗
PubMed1987

A novel acyl-CoA-binding protein from bovine liver. Effect on fatty acid synthesis.

Bovine liver was shown to contain a hitherto undescribed medium-chain acyl-CoA-binding protein. The protein co-purifies with fatty-acid-binding proteins, but was, unlike these proteins, unable to bind fatty acids. The protein induced synthesis of medium-chain acyl-CoA esters on incubation with goat mammary-gland fatty acid synthetase. The possible function of the protein is discussed.

Animals↗