Biomedical subjects

J T Rasmussen

Publications and source records attributed to J T Rasmussen.

10 recordsLinked to original sources

PubMed1997

Bovine PAS-6/7 binds alpha v beta 5 integrins and anionic phospholipids through two domains.

Bovine milk fat globule membranes are a rich source of glycoproteins PAS-6 (52 kDa) and PAS-7 (47 kDa). They are glycosylation variants sharing a common polypeptide core. The PAS-6/7 protein consists of two EGF-like domains and a tandem repeated structure with a high degree of similarity to the C1 and C2 domains found in blood-clotting factors V and VIII. The second EGF-like domain contains an RGD cell adhesion sequence with the possibility of binding integrins, while the C-terminal end of the C2-like domain contains a probable amphipathic alpha-helix. Using a PAS-6/7 column, bovine alpha v beta 5 integrin was purified from mammary gland tissue by affinity chromatography and characterized by Western blotting and N-terminal sequencing. The interaction between PAS-6/7 and the alpha v beta 5 integrin was shown to be RGD dependent. Lipid binding assays showed that PAS-6/7 binds to surfaces of phosphatidylserine, -inositol, and -glycerol, and their precursor, phosphatidic acid, but not phosphatidylcholine. Furthermore, PAS-6/7 displayed the highest affinity toward a total lipid fraction derived from the milk fat globule membrane as compared to pure phospholipids. Using Western blotting technique, PAS-6/7 was shown to be widely expressed in a number of tissues. These results show that PAS-6/7 is a common protein which can bind to membranes by two distinct mechanisms, one through affinity to integrin alpha v beta 5 and another by direct binding to phospholipids.

Amino Acid Sequence↗

PubMed1996

Structural characterization of bovine CD36 from the milk fat globule membrane.

Bovine CD36 from milk fat globule membranes was characterized and a full-length CD36 cDNA of 2772 nucleotides was isolated from a bovine mammary gland cDNA library. The deduced protein sequence contains 472 amino acid residues with 82-84% identity to the amino acid sequences of CD36 from other species. Peptides corresponding to 43% of the protein were sequenced. All eight potential N-glycosylation sites were glycosylated and the carbohydrate compositions of the individual sites were determined.

Amino Acid Sequence↗

PubMed1996

Characterization of glycoprotein PAS-6/7 from membranes of bovine milk fat globules.

Glycoprotein components PAS-6 and PAS-7 were purified from bovine milk-fat-globule membranes and the amino acid sequence of their common polypeptide core, PAS-6/7, was determined by peptide and cDNA sequencing. The cDNA encoded a signal peptide of 18 amino acid residues and a mature PAS-6/ 7 protein of 409 amino acid residues. A cDNA splice variant was identified by reverse transcription/ PCR. Results obtained by amino acid analyses, amino-acid-sequence analyses, carbohydrate-composition determinations, and MS analyses of glycopeptides revealed that both proteins were glycosylated with a carbohydrate structure that contained galactose, N-acetylgalactosamine and fucose, and which was O-linked to Ser9 in PAS-6 and to Thr16 in PAS-7. In addition, PAS-6 and PAS-7 were N-glycosylated at Asn41 with a hybrid-type-carbohydrate structure. A high-mannose glycan was N-linked to Asn209 of PAS-6. The sequence of PAS-6/7 contained two epidermal growth factor (EGF)-like domains in the N-terminal region, the second of which contained an RGD cell-adhesion sequence in an extended loop. The EGF-like domains were followed by a C-terminal tandem repeat, which showed 60-63% similarity to the C1-C2 domain of blood-clotting factors V and VIII. The disulfide bonds within the C1-C2 domain were identified.

Alternative Splicing↗

PubMed1996

Purification of the bovine xanthine oxidoreductase from milk fat globule membranes and cloning of complementary deoxyribonucleic acid.

The amino acid sequence of the bovine xanthine oxidoreductase was determined by cloning and sequencing cDNA clones encoding the enzyme. Partial amino acid sequence corresponding to 54% of the total sequence were also determined from purified bovine milk xanthine oxidoreductase, showing identity with the translated cDNA sequence. The cDNA of 4719 nucleotides included a 5' untranslated region of 96 nucleotides, an open reading frame encoding a xanthine oxidoreductase of 1332 amino acid residues, and a 3' untranslated region of 624 nucleotides including two polyadenylation signals and a poly (A) tail of 74 nucleotides. The identity between the amino acid sequence of the bovine xanthine oxidoreductase and xanthine oxidoreductase from mammalian species was 86 to 90%.

Amino Acid Sequence↗

PubMed1994

Acyl-CoA-binding protein (ACBP) can mediate intermembrane acyl-CoA transport and donate acyl-CoA for beta-oxidation and glycerolipid synthesis.

The dissociation constants for octanoyl-CoA, dodecanoyl-CoA and hexadecanoyl-CoA binding to acyl-CoA-binding protein (ACBP) were determined by using titration microcalorimetry. The KD values obtained, (0.24 +/- 0.02) x 10(-6) M, (0.65 +/- 0.2) x 10(-8) M and (0.45 +/- 0.2) x 10(-13) M respectively, were much lower than expected. ACBP was able to extract hexadecanoyl-CoA from phosphatidylcholine membranes immobilized on a nitrocellulose membrane. The acyl-CoA/ACBP complex formed was able to transport acyl-CoA to mitochondria or microsomes in suspension, or to microsomes immobilized on a nitrocellulose membrane, and to donate them to beta-oxidation or glycerolipid synthesis in mitochondria or microsomes, respectively.

Acyl Coenzyme A↗

PubMed1993

Interaction of acyl-CoA binding protein (ACBP) on processes for which acyl-CoA is a substrate, product or inhibitor.

It is shown that acyl-CoA binding protein (ACBP), in contrast with fatty acid binding protein (FABP), stimulates the synthesis of long-chain acyl-CoA esters by mitochondria. ACBP effectively opposes the product feedback inhibition of the long-chain acyl-CoA synthetase by sequestration of the synthesized acyl-CoA esters. Feedback inhibition of microsomal long-chain acyl-CoA synthesis could not be observed, due to the formation of small acyl-CoA binding vesicles during preparation and/or incubation. Microsomal membrane preparations are therefore unsuitable for studying feedback inhibition of long-chain acyl-CoA synthesis. ACBP was found to have a strong attenuating effect on the long-chain acyl-CoA inhibition of both acetyl-CoA carboxylase and mitochondrial adenine nucleotide translocase. Both processes were unaffected by the presence of long-chain acyl-CoA esters when the ratio of long-chain acyl-CoA to ACBP was below 1, independent of the acyl-CoA concentration used. It is therefore not the acyl-CoA concentration as such which is important from a regulatory point of view, but the ratio of acyl-CoA to ACBP. The cytosolic ratio of long-chain acyl-CoA to ACBP was shown to be well below 1 in the liver of fed rats. ACBP could compete with the triacylglycerol-synthesizing pathway, but not with the phospholipid-synthesizing enzymes, for acyl-CoA esters. Furthermore, in contrast with FABP, ACBP was able to protect long-chain acyl-CoA esters against hydrolysis by microsomal acyl-CoA hydrolases. The results suggest that long-chain acyl-CoA esters synthesized for either triacylglycerol synthesis or beta-oxidation have to pass through the acyl-CoA/ACBP pool before utilization. This means that acyl-CoA synthesized by microsomal or mitochondrial synthetases is uniformly available in the cell. It is suggested that ACBP has a duel function in (1) creating a cytosolic pool of acyl-CoA protected against acyl-CoA hydrolases, and (2) protecting vital cellular processes from being affected by long-chain acyl-CoA esters.

Acyl Coenzyme A↗

PubMed1992

Purification and characterization of variants of acyl-CoA-binding protein in the bovine liver.

Four differently modified forms of acyl-CoA-binding protein (ACBP) were identified in ACBP purified from bovine liver. The majority of the purified ACBP was focused at pH 5.9 in isoelectric focusing and could be shown to be N-acetylated ACBP without any further modifications. Two minor peaks were focused at pH 5.25 and 4.85 respectively. Mass spectrometry and sequence determination showed that the pI 5.25 form was acetylated at Lys18 and that the pI 4.85 form was malonylated in the same position. Furthermore, it could be shown that non-enzymic glycosylation occurred during purification. The acetylated and malonylated variants of ACBP were only found in adult cattle.

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↗

PubMed1985

[Adder bites].

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Adolescent↗

PubMedDate not supplied

The function of acyl-CoA-binding protein (ACBP)/diazepam binding inhibitor (DBI).

Acyl-CoA-binding protein has been isolated independently by five different groups based on its ability to (1) displace diazepam from the GABAA receptor, (2) affect cell growth, (3) induce medium-chain acyl-CoA-ester synthesis, (4) stimulate steroid hormone synthesis, and (5) affect glucose-induced insulin secretion. In this survey evidence is presented to show that ACBP is able to act as an intracellular acyl-CoA transporter and acyl-CoA pool former. The rat ACBP genomic gene consists of 4 exons and is actively expressed in all tissues tested with highest concentration being found in liver. ACBP consists of 86 amino acid residues and contains 4 alpha-helices which are folded into a boomerang type of structure with alpha-helices 1, 2 and 4 in the one arm and alpha-helix 3 and an open loop in the other arm of the boomerang. ACBP is able to stimulate mitochondrial acyl-CoA synthetase by removing acyl-CoA esters from the enzyme. ACBP is also able to desorb acyl-CoA esters from immobilized membranes and transport and deliver these for mitochondrial beta-oxidation. ACBP efficiently protects acetyl-CoA carboxylase and the mitochondrial ADP/ATP translocase against acyl-CoA inhibition. Finally, ACBP is shown to be able to act as an intracellular acyl-CoA pool former by overexpression in yeast. The possible role of ACBP in lipid metabolism is discussed.

Acyl Coenzyme A↗