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T Peters

Publications and source records attributed to T Peters.

At least 271 records · Page 15Linked to original sources
PubMed1977

Immunochemical studies of fragments of bovine serum albumin.

Antigenic properties of 14 fragments of bovine albumin were measured using antisera to albumin and to two of its fragments. All seven fragments larger than 21,000 daltons formed immune precipitates. Although immune precipitates were not formed with smaller fragments, inhibition tests indicated the presence of antigenic sites on several of these fragments as well. The results predict the occurrence of six or more antigenic determinants and allow assignment of their positions in the parent molecule. These sites are distributed along the entire protein chain, with the sites of greatest antibody affinity situated in the COOH-terminal region. Evidence is presented that some sites are homologous, reacting with the same populations of antibodies, and that other sites are unique, binding to an exclusive population of antibodies.

Antibodies↗
PubMed1977

Interdependence of ion transport and the action of quabain in heart muscle.

1 The influence of ouabain (0.4 muM) on contractile force and cellular Na and K concentrations was investigated in isolated left atria of the guinea-pig at rest and at different beat frequencies. Simultaneously the binding of ouabain to the tissue was determined.2 Strict dependence of rates of onset of positive iontropic action and of binding of ouabain on beat frequency are limited to conditions where no alterations of cellular Na and K concentrations occur. A correlation was observed between sodium flux per unit time and the development of positive inotropism and binding to the receptors of ouabain.3 Ouabain exerts its positive inotropic effect without affecting the intracellular Na and K concentrations in spite of the fact that under these conditions even the majority of binding sites, i.e. Na-K-adenosine triphosphatases (Na-K-ATPases), are occupied by the drug. The positive inotropic effect may be explained by a ouabain-induced conformational alteration of the Na-K-ATPase which leads to structural alterations of the plasmalemma connected with an increased availability of coupling calcium.4 Increasing the frequency of stimulation over a critical value, which appears to be determined by an overloading of the Na pump, induces a decrease in contractile force, cellular accumulation of Na and loss of K, and eventually contracture.5 The rate of binding of ouabain appears to depend on the actual concentration of particular conformations of the Na-K-ATPase with high affinity for ouabain. These conformations transiently occur during a pumping cycle and their concentration may therefore be dependent on the frequency of cycling which in turn is determined by the frequency of contraction.6 Ouabain can easily be washed out from the tissue irrespective of the condition of the muscle. If, however, the intracellular Na and K homeostasis is impaired, the inhibition of the pump persists even if ouabain is released from the binding sites upon wash-out. It is suggested that the inhibition of the pump is maintained by an increased intracellular Ca ion concentration and a depletion of ATP.7 A kinetic model is proposed for the interaction between cardiac glycosides and the Na-K-ATPase in intact heart muscle cells.

Animals↗
PubMed1977

Serum albumin: recent progress in the understanding of its structure and biosynthesis.

Major discoveries have been made in the past few years on the structure and mode of biosynthesis of serum albumin. The complete amino acid sequence of this protein has been determined, and its covalent structure shown to be a single peptide chain grouped into a series of nine disulfide-bonded loops. These loops appear to associate into three similar domains. By study of isolated fragments of the molecule it can be demonstrated that the binding of billirubin and the primary binding of long-chain fatty acids are functions of separate domains. The biosynthesis of albumin has been found to involve a precursor form, termed "proalbumin", in which a basic hexapeptide is attached to the amino end of the chain. Similar precursor forms are now known to have a role in the formation of other secreted proteins, but in the case of albumin the purpose of the additional peptide is not clear. Clinical methodology for albumin assay has advanced but little despite--or perhaps in part because of--the increasing use of automation. Hope for improvement is foreseen in the advent of immunochemical procedures and in a better understanding of the specificity of dye-binding reactions.

Amino Acid Sequence↗
PubMed1976

Determination of the number and relative position of tryptophan residues in various albumins.

A technique is described by which both the numbers of tryptophan residues and their approximate locations in the peptide chain of a protein can be determined by cleavage with N-bromosuccinimide followed by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. The number of new peptide bands appearing in the gel is a function of the number of tryptophan residues, and the relative migration of the bands permits calculation of peptide molecular weights and an estimation of the positions of the tryptophan residues in the peptide chain. The technique uses a sample of about 0.5 mg and is suitable for any protein that contains a small number of tryptophan residues. These are the very specimens that are difficult to assay accurately for tryptophan by spectrophotometric or colorimetric methods. Tryptophan residues which are within about 20 residues of the ends of the peptide chain or of each other would not be detected. The specificity of the cleavage with N-bromosuccinimide was ascertained by utilizing human serum albumin, which is known to have a single tryptophan residue at position 214. The technique was then applied to a comparative study of the numbers and locations of tryptophans in the serum albumins of 16 species, namely 11 mammals, three birds and two amphibians. The number of tryptophan residues were confirmed by an independent colorimetric method. All of the mammalian albumins contained a tryptophan residue near position 213. The three avian albumins examined have no tryptophan. Frog and toad albumins contained two tryptophan residues, which appear to be situated at different positions from those in mammalian albumins.

Amino Acid Sequence↗
PubMed1976

On the sarcolemmal site of action of cardiac glycosides.

An electron microscopic study of the guinea pig myocardial cell was conducted. By the use of LaC13, two morphologically distinct tubular systems could be demonstrated. The larger one represents the transverse tubular system which originates from the plasma membrane and is continous with the extracellular space (ECS). In the heart muscle cell it forms a three-dimensional network and it closely apposed to the myofilaments at the level of the Z and I bands. A comparatively small and sparsely developed tubular system which is not accessible from the ECS represents the sarcoplasmic reticulum (SR). By means of sucrose-density centrifugation in a discontinuous gradient two main microsomal fractions were obtained (F1 and F3). The pre-existing structure of F1 could be identified as the transverse tubular system, whereas F3 originates from the SR. The morphological features (e. g., an enclosed basement membrane) and the fact that after perfusion of hearts with [3H] inulin and preparation of microsomes the ECS marker is almost completely retained in F1 indicate that upon fractionation and vesiculation inside-out vesicles are formed which trap the former extracellular fluid. Moreover, the former extracellular surface is hidden and no longer accessible for membrane-impermeable compounds. After perfusion of hearts with [3H] ouabain and fractionation and centrifugation the radioactive material was found to accumulate in F1, the kinetics being identical with that of binding to the intact tissue and with the time course of the inotropic action of ouabain. The inside-out vesicles derived from the plasma membrane are characterized by the presence of a (Na+-K+)-ATPase activity, an outward Ca pump, a high binding capacity for Ca, and a low Ca pereability. Since the (Na+-K+)-ATPase is known to react with cardiac glycosides (CG) at the outer cell surface it was not surprising to find a complete lack of inhibition of the enzyme by the membrane-impermeable CG ouabain if administered to the intact sarcolemmal microsome. After disruption of the microsomes, however, a considerable inhibition of the (Na+-K+)-ATPase became demonstrable. Similarly, the Ca permeability of the plasma membranes could only be enhanced by CG if interacting with the former outside. Although ouabain again failed to exert any action, the membrane permeable digoxin increased the Ca pereability of the intact vesicular membrane. The rate of Ca transport as an indicator of the Ca pump activity remained unaffected by CG provided from either side of the membrane. The passive Ca binding to the plasma membrane, which results in a concentration up to 5 mM in this structure, is thought to represent the Ca pool essential for excitation-contraction coupling. The CG are thought to alter the Ca binding in this pool, thus rendering depolarization more effective in releasing Ca++.

Adenosine Triphosphatases↗
PubMed1975

Fragments of bovine serum albumin produced by limited proteolysis. Conformation and ligand binding.

Twelve fragments of bovine serum albumin, isolated following limited tryptic or peptic hydrolysis, have been studied to define secondary structure and locate ligand-binding sites. Based on circular dichroism, the conformational pattern of albumin (68% alpha helix and 18% beta structure) is substantially retained by individual fragments, indicating that secondary configuration is locally determined and is not destroyed during the cleavage process nor during fragment purification. The strong bilirubin-binding site of bovine serum albumin is present in 3 of the 12 fragments. Residues 186-238 are common to the three fragments and absent from those fragments which do not bind bilirubin; consequently the strong bilirubin-binding site is suggested to involve this region. By similar reasoning, the presence of palmitate-binding sites in some fragments and not in others indicates that the three strongest sites for the binding of palmitate are located in the carboxyl-terminal two-thirds of the molecule. The first site (KA approximately 2 X 10(7) M-1) is suggested as residues 377-503; the second site (KA approximately 8 X 10(6) M-1), residues 239-306; the third site (KA approximately 2 X 10(6) M-1), residues 307-377. Bromocresol Green, a reagent used in the assay of ablumin, was bound by fragments rougly in proportion to their size but showed particular affinity for the region of the strong bilirubin-binding site. The fluorescent probe, 8-anilino-1-naphthalensulfonate, was in general bound by large fragments, supporting the concept that this ligand is held principally in clefts between domains of the macromolecule.

Anilino Naphthalenesulfonates↗
PubMed1975

Fragments of bovine serum albumin produced by limited proteolysis. Isolation and characterization of peptic fragments.

Five new fragments of bovine serum albumin have been isolated following limited peptic hydrolysis. These fragments, and the two peptic fragments previously described by King (King, T.P. (1973), Arch. Biochem. Biophys. 156, 509), were positioned within the albumin sequence published by Brown (Brown, J.R. (1975), Fed. Proc., Fed. Am. Soc. Exp. Biol. 34, 591) on the basis of molecular weight, amino acid composition, and amino- and carboxyl-terminal sequences. The fragments correspond to residues 1-385, 1-306, 307-581, 49-185, 186-306, 307-385, and 353-503 in the albumin sequence. These peptides are likely to be native in structure since disulfide bonds were not cleaved during their preparation. In each case the amino acid composition and terminal sequences have confirmed the bovine serum albumin sequence and disulfide bridging pattern proposed by Brown, and the offer further proof that bovine albumin is composed of a series of nine independent loops. These fragments should be useful in elucidating the structure-function relationships of albumin.

Amino Acid Sequence↗
PubMed1975

Fragments of bovine serum albumin produced by limited proteolysis. Isolation and characterization of tryptic fragments.

Several fragments of bovine serum albumin have been isolated following limited tryptic hydrolysis and their positions then determined in the bovine serum albumin sequence published by J. R. Brown ((1975), Fed. Proc., Fed. Am. Soc. Exp. Biol. 34, 591). When bovine serum albumin was coupled to palmityl-aminoethylamino-agarose and digested with trypsin, two fragments were obtained: (a) peptide 115-184, containing the highly aromatic disulfide loop 3 of Brown's model, and (b) a larger fragment, residues 377-581, containing disulfide loops 7-9. This fragment constitutes the third of the three domains of the albumin molecule. From bovine serum albumin digested in solution, peptide 115-184 was again obtained, as well as (c) a 39,000-dalton fragment identified as residues 198-581, loops 4-9 of the second and third domains, but with a long, tryptophan-containing segment 204-238 missing from loop 4. The ability to isolate these fragments without cleaving disulfide bridges is partial confirmation of the proposed model of bovine serum albumin as a series of nine independent loops.

Amino Acid Sequence↗
PubMed1975

Alcoholism.

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Alcoholism↗
PubMed1975

Influence of ouabain and dihydroouabain on the circular dichroism of cardiac plasmalemmal microsomes.

1. The influence of ouabain on the tertiary structure of cardiac plasmalemmal proteins was investigated by means of circular dichroism measurement. Purified plasmalemmal microsomes were obtained by sucrose gradient centrifugation. The CD-spectra of the membranal proteins were shifted to the red and the amplitudes were smaller than those of the same proteins after solubilization. 2. Ouabain induced an increase of the ellipticity bands at 210 and 222 nm of about 50% above the level yielded with microsomes after sonication. At 222 nm ouabain exhibited the half maximum effect at a concentration of 5 X 10(-9) M. The effect could, however, only be exerted if the inside of the microsomes was exposed to ouabain by sonication, thus reflecting the inside-out nature of the plasmalemmal microsomes. 3. The high specificity of the ouabain effect was underlined by the following experiments: a) Dihydroouabain, a much less cardioactive derivative of ouabain proved to be ineffective in corresponding concentrations, b) ouabain had no influence upon the CD spectrum of microsomes derived from cardiac sarcoplasmic reticulum, c) a detergent-like action of ouabain underlying the observed effect can be excluded since highly active tensides, i.e. desoxycholate and dodecylsulfate, only influence the CD spectra at concentrations exceeding 10(-3) M, d) electronmicrographs of microsomes exposed to ouabain demonstrated no alteration of either the appearance or size of the microsomes. 4. The magnitude of the observed ouabain effect indicates that a large portion of the membrane-bound proteins is involved. The number of binding sites and their isolated structural alteration induced by ouabain are not sufficient to account quantitatively for the enhanced amplitudes of the CD spctra. This suggests that ouabain evokes structural changes of membrane proteins different from actual binding sites. It seems, therefore highly improbable that changes of the Na-K-ATPase present in the plasmalemmal microsomes are responsible for the observed effect.

Animals↗