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Biomedical subjects

H Olesen

Publications and source records attributed to H Olesen.

At least 55 records · Page 3Linked to original sources
PubMed1978

Primary structure of human intrinsic factor: progress report on cyanogen bromide fragmentation.

Human intrinsic factor purified by labile ligand affinity chromatography was cleaved with cyanogen bromide and fractionated by gel filtration. Four of the fragments were purified and sequenced to a total of eighty-four amino acid residues. Including the N-terminal amino acids this amounts to one third of the total amino acid sequence of human intrinsic factor. One of the fragments contained a tyrosine labelled only on iodination of intrinsic factor devoid of cobalamin.

Amino Acid Sequence↗
PubMed1977

Purification and characterization of rabbit transcobalamin II.

Rabbit transcobalamin II has been purified by labile ligand affinity chromatography and G-200 Sephadex gel filtration. Structural studies indicate Stokes' radii of 2.7 nm and 3.0 nm for transocobalamin II saturated and unsaturated with cobalamin. The amino acid content of the protein is very similar to that of human transcobalamin II (Allen, R. H. (1975) Prog. Hematol. 9, 59-84). The aminoterminal sequence for transcobalamin II is reported for the first time: Glu-Ile-Cys-Gly-Val-Pro-Lys-Val-Asp-Ser-Glu-Leu-Val-Glu-Lys-Leu-Gly-Gln-Arg-Leu-Leu-Pro-(Trp)-Met-Thr). The ultraviolet and circular dichroic spectra of aquo-, hydroxo-, azido- and cyanocobalamin bound to rabbit transcobalamin II are described. On complex formation the molar absorption of the cobalamins increases and the major bands shift to longer wavelengths. The spectra are little affected by change in the fifth ligand, which indicates that the electron density around the cobalt atom is kept fairly constant by the transcobalamin II molecule. This is in contrast to the observations for the same cobalamins attached to human intrinsic factor and human transcobalamin I (Nexo, E. and Olesen, H. (1976) Biochim. Biophys. Acta 446, 143-150).

Amino Acid Sequence↗
PubMed1977

Cobalamin binding proteins in stomach and serum from various animal species data for B12 binding capacities and molecular sizes of the binding proteins.

1. The unsaturated cobalamin-binding capacity of stomach mucosa and serum from 37 animals and the size of the binders have been measured. 2. The binding capacity in stomach mucosa was from 1 to 600 nmole kg-1 wet wt, the highest values occurring in pig, guinea pig, porpoise and earthworm. In serum it varied from 0.4 to 270 nmole 1(-1), the highest values occurring in duck, grass snake, toad and spiny dogfish. 3. The size in terms of Stokes radius of the cobalamin binders in stomach mucosa varied from 1 nm in hagfish (Mr approximately 14,000) to 7 nm in lamprey (Mr approximately 210,000). In serum it was from 1.4 nm (Mr approximately 17,000) to 7.4 nm (Mr approximately 240,000) both in frog.

Animals↗
PubMed1976

An improved procedure for automated Edman degradation used for determination of the N-terminal amino acid sequence of human transcobalamin I and human intrinsic factor.

An improved procedure for automated Edman degradation is presented. Three programs are described, one with double cleavage and two with single cleavage. The programs presented are characterized by a reversed delivery scheme for buffer and phenyl isothiocyanate, and by reduced cleavage times. The modified procedures applied on automated Edman degradation of the vitamin B12-binding proteins human transcobalamin I and human intrinsic factor, containing approximately 390 and 350 amino residues respectively, gave the following N-terminal amino acid sequences: Human transcobalamin I Glu-Ile-Cys-Glu-Val-Ser-Glu-Glu-Asn-Tyr-Ile-Arg-Leu-Lys-Pro-Leu-Leu-Asn-Thr-Met-Ile-Gln-Ser-Asn-Tyr-Asn-?-Gly- Human intrinsic factor Ser-Thr-Gln-Thr-Gln-Ser-Ser-Cys-Ser-Val-Pro-Ser-Ala-Gln-Glu-Pro-Leu-Val-Asn-Gly-Ile-Gln-?-Leu-Met-Glu-Thr- The background accumulation seems to be related not only to the length of the polypeptide chain being degraded, but also to the content of serine (and possibly threonine). A possible N leads to O acyl shift during the cleavage is a tentative explanation. The programs here represented lead to a significant reduction in background compared to conventional programs and allowed considerable prolongation of the degradations.

Amino Acid Sequence↗
PubMed1976

Changes in the ultraviolet and circular dichroism spectra of aquo-, hydroxy-, azido-, and cyanocobalamin when bound to human intrinsic factor or human transcobalamin I.

The ultraviolet and the circular dichroic spectra of aquo-, hydroxy-, azido-, and cyanocobalamin free or bound to purified human intrinsic factor or purified human transcobalamin I were recorded. Except for azidocobalamin-transcobalamin I, the molar absorption for the gamma1-band in the ultraviolet spectra increased with a factor between 1.2 and 1.4 when the cobalamins were bound to protein. The ultraviolet spectrum of azidocobalamin-transcobalamin I changed so that the gamma2-band became the most intense. Minor changes were observed in the other ultraviolet spectra. The most prominent change in the CD-spectra of protein bound cobalamins was the increase in negative elipticity above 400 nm. This increase was most intense for cyano- and azidocobalamin-transcobalamin I. The study emphasizes that the mechanism by which human intrinsic factor and human transcobalamin I bind cobalamins differ.

Binding Sites↗
PubMed1976

Folic acid binding by human plasma albumin.

Binding of [3H]folate to pure human plasma albumin was studied by Sephadex G-200 gel filtration in a steady-state system. The experiments showed the presence of two binding sites per molecule of albumin and an equilibrium constant of 0.9x10(3) 1/mol. With normal human plasma, only albumin bound exogenous [3H]folate with nearly the same equilibrium constant. In human blood plasma at concentrations of less than 10(-5) mol/1, 50% of folate was free, and 50% was bound to albumin. Binding was maximal at about pH 6 and negligible above pH 8 and below pH 4.5. Neither human transferrin nor Cohn fraction II was able to bind [3H]folate.

Binding Sites↗
PubMed1975

Characterization of a cobalamin-binding plasma protein from a patient with hepatoma.

A cobalamin-binding protein has been purified by affinity chromatography from plasma of a patient with hepatoma and a 10,000-fold increase in the concentration of the plasma cobalamin-binding capacity. The protein behaved as normal transcobalamin I in gel filtration, agar gel electrophoresis, immunoelectrophoresis, precipitation by ammonium sulphate, and cobalamin-binding studies. The protein contained 38 per cent carbohydrate, and the relative molecular mass based on amino acid and carbohydrate analyses was 69,000. The molar absorption coefficient of cyanocobalamin bound to the protein was determined to be 36,000 at 362 nm. On amino acid sequencing, one amino terminal was found, and the first 13 residues were determined as Glu-Ile-Ser/Cys-Glu-Val-Ser/Cys-Glu-Glu-Asx-Tyr-Ile-Arg-Leu/Ile.

Amino Acid Sequence↗
PubMed1975

A rare case of megaloblastic anaemia caused by disturbances in the plasma cobalamin binding proteins in a patient with hepatocellular carcinoma.

A patient with hepatocellular carcinoma, megaloblastic anaemia and increased concentration of serum cobalamin is described. Plasma TC I was increased to 10,000 times the normal concentration, thus explaining the increased concentration of serum cobalamin and a false Schilling test. The increase in plasma TC I in concurrence with undetectable amounts of plasma TC II was a likely explanation for the anaemia. The electron microscopic picture of the hepatocellular carcinoma was in accordance with TC I being produced by the tumour cells.

Anemia, Macrocytic↗
PubMed1975

Solid-phase cobalamin assay using cobalamin-binding protein from dog stomach.

Ninety-five samples from 42 animals were studied for the presence of a cobalamin-binding protein fulfilling the criteria of occurring in major quantities and being homogeneous regarding size and binding constant. The binder from dog stomach thus found was made insoluble by coupling to bromoacetyl-cellulose and used for solid-phase assay of serum cobalamins. Equilibrium between free and bound radioactive cobalamin was unaffected by centrifugation of the samples, thus allowing the straightforward use of the Scatchard equation for calculation of results. The precision of the method was 0.05 to 0.10 at concentrations above 100 pmolX1(-1), the sensitivity was about 30 pmolX1(-1), the accuracy could be based on aqueous solutions of cyanocobalamin, and the reference interval was as for the Lactobacillus leichmannii method, i.e. 160-480 pmolX1(-1).

Adolescent↗