Showing papers on "Myoglobin published in 1969"
TL;DR: A rapid refinement procedure capable of deriving the stable conformation of a macromolecule from experimental model co-ordinates is presented and a set of non-bonded potential functions applicable to the equilibrium of a folded protein in an aqueous medium is described and tested on myoglobin.
409 citations
TL;DR: X-ray analysis of sperm whale myoglobin at 2·0 Å resolution provided the first solution of the structure of a protein, which consists of only one polypeptide chain of 153 residues and a single haem.
Abstract: Haemoglobin is the respiratory protein of the red blood cells which carries oxygen from the lungs to the tissues and facilitates, both directly and indirectly, the return transport of carbon dioxide. Mammalian haemoglobin has a molecular weight of 64500 and contains two pairs of polypeptide chains: the α -chains with 141 amino acid residues each and the β -chains with 146. Each chain is combined with one haem. Myoglobin, the oxygen carrier of muscle, is closely related to haemoglobin, but has a simpler constitution: it consists of only one polypeptide chain of 153 residues and a single haem. The amino acid sequences of the myoglobins and haemoglobins of man and of several animals have been determined (Dayhoff & Eck 1968). By means of the method of isomorphous replacement with heavy atoms, X-ray analysis of sperm whale myoglobin at 2·0 A resolution provided the first solution of the structure of a protein (Kendrew et al . 1960; Watson 1969). All but 21 of its 153 residues form part of helices; over most of their length these helices have conformations closely resembling the right-handed α -helix of Pauling & Corey (1951). The chain is divided into 8 helical segments, separated by corners or non-helical regions. Together these form a kind of basket into which the haem group fits neatly, so that only its propionic acid side-chains protrude into the surrounding liquid (figures 1, 2). X-ray analysis at 5·5 A resolution showed each chain of horse haemoglobin to be folded in much the same way as the single chain of sperm whale myoglobin. The 4 chains are arranged tetrahedrally, each carrying one haem in a pocket near the protein surface. The chemically identical halves of the molecule are related by a twofold symmetry axis (figure 3, plate 18; Cullis et al . 1962).
156 citations
TL;DR: Several sequences which could be previously deduced from the study of split products after cyanogen bromide treatment were confirmed, and the specificity of chymotrypsin towards certain types of peptide bonds is discussed.
Abstract: The complete sequence (153 amino acids) of horse heart myoglobin has been established.
The sequence of a peptide isolated from chymotrypsin hydrolyzates of globin allowed to fill a gap in the tentative sequence previously proposed; this peptide was studied by means of pepsin hydrolysis, action of N-bromosuccinimide on histidyl bonds, and Edman degradation method associated with dansylation.
After hydrolysis of globin by chymotrypsin treated by TLCK, the same major peptides were found as after hydrolysis by non-treated chymotrypsin. These peptides were identified by ion-exchange resins and bidimensional paper chromatography, and also by the determination of their amino-acid composition.
The suppression of secondary cuts explains the presence of new peptides, whose the composition and N-terminal sequences were determined. It was then possible to confirm several sequences which could be previously deduced from the study of split products after cyanogen bromide treatment. The specificity of chymotrypsin towards certain types of peptide bonds is discussed.
Horse myoglobin, as compared with sperm whale myoglobin, contains 18 differences: 17 substitutions and one inversion. The major part of the substitutions are located in N- and C-terminal sequences; they are all punctiform, resulting from the replacement of only one base in each codon.
129 citations
TL;DR: Manganese porphyrin-containing myoglobin neither formed peroxide compounds nor exhibited peroxidase activity under comparable conditions, and these myoglobin derivatives and their dithionite-reduced compounds did not form complexes with oxygen and carbon monoxide.
124 citations
TL;DR: The effectiveness of these denaturing agents on sperm-whale myoglobin increases with increasing chain length and hydrocarbon content, as expected in view of the disorganization of the hydrophobic interior of this protein.
Abstract: As judged from the midpoints of the denaturation transition of 31 water-miscible alcohols, ureas, and amides, the effectiveness of these denaturing agents on sperm-whale myoglobin increases with increasing chain length and hydrocarbon content, as expected in view of the disorganization of the hydrophobic interior of this protein. Increase in the hydroxyl content, blocking of the functional amino groups of the ureas and amides by alkyl substitution, and branching of the hydrocarbon portion of the denaturants are of less importance in determining the effectiveness of the denaturants.
93 citations
TL;DR: A preliminary analysis of myoglobin proves that neutron diffraction analysis of proteins is feasible and should reveal the position of fixed hydrogen atoms.
Abstract: A preliminary analysis of myoglobin proves that neutron diffraction analysis of proteins is feasible and should reveal the position of fixed hydrogen atoms.
76 citations
TL;DR: Evidence was found for the importance of an “opening”-dependent pathway for slowly exchanging, H-bonded hydrogens of myoglobin, as opposed to some direct exchange mechanism not dependent on conformational movement.
70 citations
TL;DR: The results show that binding of oxygen to the isolated α and β subunits, as well as to sperm whale myoglobin, is kinetically a simple process, in that the reaction follows bimolecular kinetics.
64 citations
TL;DR: The three-dimensional structure of metmyoglobin from the common seal has been determined at 2.5 A resolution using the isomorphous replacement technique using two derivatives, the mercuri-iodide and the aurichloride, and the molecule is described in detail.
63 citations
53 citations
TL;DR: The hypothesis is developed that the buffer-binding site may lie between arginine-45 and histidine-64 and a reasonable mechanism for the buffer catalysis is proposed.
TL;DR: The optical rotatory properties of the fully formed complex with l-valyl-l-leucyl-seryl- l-glutamylglycine, corresponding to the NH2-terminal sequence in sperm whale myoglobin, can be distinguished qualitatively from that of complexes with histidine-containing peptides.
TL;DR: The sequence of human myoglobin appears to be accommodated easily into the proposed three-dimensional structure of whale myoglobin, and large differences in the conformation of these two myoglobins cannot be expected.
Journal Article•
TL;DR: Comparing the dielectric increment of native myoglobin and its change during the reaction with bromo acetate with dipole moments calculated according to the known coordinates of the charged groups of the molecule shows that in myoglobin only the permanent dipole moment due to these charged groups is important, and that contributions from other possible sources remain within the limits of experimental error.
Abstract: This paper is concerned with the molecular origin of the dipole moment of sperm whale myoglobin as it can be calculated from the dielectric dispersion at 1 Mcps on the basis of a mechanism of orientational polarization. It was possible to compare the dielectric increment of native myoglobin and its change during the reaction with bromo acetate with dipole moments calculated according to the known coordinates of the charged groups of the molecule. The agreement between the two shows that in myoglobin only the permanent dipole moment due to these charged groups is important, and that contributions from other possible sources remain within the limits of experimental error.
TL;DR: Results indicate that the addition of the ligands to these two proteins causes the exclusion of solvent water from otherwise exchangeable protein hydrogen atoms, suggesting some combination of direct shielding of the protein from the solvent by the ligand, and changes in conformation and motility.
TL;DR: Dielectric dispersion measurements with aqueous solutions of hemoglobin and myoglobin have been performed and the results are analyzed in terms of an orientational polarization mechanism.
Abstract: Dielectric dispersion measurements with aqueous solutions of hemoglobin and myoglobin have been performed in the frequency range from 100 kcps to 15 Mcps. The influence of preparation, particle size, and solvent conditions was studied. The results are analyzed in terms of an orientational polarization mechanism.
TL;DR: There was a difference in the odours accompanying the development of rancidity after the addition of free Fe++ and hemoglobin-bound Fe++, and certain free amino acids, notably tryptophane and proline, also had an inhibitory action, whereas other amino acids had a prooxidant effect.
Abstract: Hemoglobin, catalase, myoglobin, and inorganic iron were added to blended muscle from cod, flounder, scallops, and lobsters to determine the effects of these various forms of iron on the oxidation ...
TL;DR: The results confirm that the methionine residues (at positions 55 and 131) are not located in antigenic reactive regions in myoglobin, and the myoglobin derivative prepared by recombination of modified apomyoglobin with ferriheme possessed spectral and sedimentation properties that were similar to those of the native protein.
TL;DR: Comparisons of the hemoglobin and myoglobin data indicate a somewhat greater degree of burial of the tryptophyls in hemoglobin than in myoglobin, and corrections for the heme-contribution to the difference spectra in the 270–295-mμ aromatic region have been suggested.
TL;DR: The electronic structure of the iron atom in heme, which is the well-known prosthetic group of hemoproteins, is discussed and ligand field theory is used, which has proved very effective in theoretical interpretations of energy levels and other electronic properties of coordination compounds of metallic ions.
Abstract: In the present paper I should l i e to discuss the electronic structure of the iron atom in heme, which is the well-known prosthetic group of hemoproteins. Since heme is a molecule consisting of a porphyrin and an Fe atom, the problem of the electronic structure of the Fe atom in heme is a part of the problem of the electronic structure of hemes. Many experimental results, however, particularly those of magnetic measuremWs, can be explained and discussed from the atomic viewpoint, in which the Fe atom or ion is considered to be subjected to electrostatic and other influences due to surrounding atoms such as the pyrrole and imidazole nitrogens. We can use ligand field theory, which has proved very effective in theoretical interpretations of energy levels and other electronic properties of coordination compounds of metallic ions. The heme found in Hb and Mb has the structure shown in FIGURE 1 ;the porphyrin of this heme is called protoporphyrin, and has two vinyl groups and two propionic acid groups, as well as methyl groups, attached to peripheral carbon atoms. Pi electrons of vinyl groups are conjugated with those of the main porphyrin ring. If we disregard these “tails,” the porphyrin and the heme possess tetragonal symmetry. The porphyrin is essentially planar, but there are evidences from x-ray analysis of hemes and myoglobin tha: the Fe atom is sometimes located above the porphyrin plane by as much as 1/2 A. The geometry of hemin chloride, separated from protein, has been measured in detail by Konig’ by the x-ray diffraction method, and the result is shown in FIGURE 2. This shows that the Fe atom is actually out of the porphyrin plane, and the symmetry of the molecule viewed from the Fe atom is approximately C In the following, a Cartesian coordinate system is introduced, with its origin at Fe nucleus, z axis perpendicular to the porphyrin plane, and x, y axes parallel to lines connecting pyrrole nitrogens, which are located diagonally opposite. These four pyrrole nitrogen atoms constitute the four ligands of the Fe atom under consideration. In the case of the native hemes in which we are interested, the Fe atom is further coordinated by another nitrogen atom of the imidazole of histidine. This nitrogen atom is the fifth ligand, and is situated approximately on the negative z axis. The plane of the imidazole ring is roughly perpendicular to the porphyrin plane, and the tetragonal symmetry is reduced, if we take the imidazole into account. Furthermore, at the sixth coordination point on the positive z axis, different kinds of small molecules and atomic ions can be coordinated, at least in myoglobin and hemoglobin. The reversible attachment of oxygen molecule at the sixth position is important in the physiological function of these molecules. Now, hemes can include the reduced and oxydized forms. The Fe atom exists in ferrous states in the reduced form and in ferric states in the oxidized form. The following abreviations are used for hemoglobins and myoglobins: Hb(FeZ+)X, for the hemoglobin whose hemes are in reduced form, Hb(FeS+)X for the oxidized form, and similar designations for myoglobins. Here X denotes the ligand which
TL;DR: The radular muscle myoglobin of the gastropod mollusc Buccinum undatum has been purified and, when reacted with excess p-hydroxymercuribenzoate (PMB), a single derivative of molecular weight 16,900 is formed.
TL;DR: Four of the 9 histidyl residues cannot be carboxymethylated in native human myoglobin, to be expected if certain of the imidazole side chains are involved in internal bonding as in the case of sperm whale myoglobin.
TL;DR: It has been suggested that the minor components which amount to not more than 10–15 per cent may be artefactual and reflect no more than stages of unfolding of the myoglobin polypeptide chain3a.
Abstract: ON starch or acrylamide gel electrophoresis, myoglobin divides into one major and one or more minor fractions. The major component—which may divide into two parts depending on the state of the haem1—has been designated Mb+ by Boyer, Fainer and Naughton2; and it has been suggested that the minor components which amount to not more than 10–15 per cent may be artefactual3 and reflect no more than stages of unfolding of the myoglobin polypeptide chain3a.
TL;DR: The combination of reduced polysome content, and reduced efficiency, may account for the reduced synthetic ability of adult muscle, for myoglobin, compared to immature muscle.
TL;DR: A three-dimensional electron density map has been obtained by calculating phases for a whale myoglobin molecule correctly located in the seal myoglobin cell and applying these to the observed seal structure amplitudes and indicates good agreement between the two investigations.
TL;DR: The n.r.m. halide probe technique is shown to be a sensitive method for detecting the binding of Cl− and Hg2+ to proteins and the direct binding of chloride ions to proteins has been demonstrated for the first time by this technique.
Abstract: The n.m.r. halide probe technique is shown to be a sensitive method for detecting the binding of Cl− and Hg2+ to proteins. The direct binding of chloride ions to proteins has been demonstrated for the first time by this technique. There appears to be only a small amount of chloride binding to horseradish peroxidase and to its apoprotein in basic aqueous solutions, but the binding increases markedly as the pH is lowered, indicating that the chloride is binding nonspecifically to positively charged regions on the protein. HgCl2 was found to bind to sperm whale myoglobin in increasing amounts as the pH was raised above 7, indicating that it may be binding to regions of negative charge on the protein. Use of the halide-ion probe technique as a means of detection of reactive sulfhydryl groups by HgCl2 titration led to the finding that there is one reactive sulfhydryl group in peroxidase, and that the rotational correlation time for the peroxidase–HgCl2 complex may be caused by rotation of the segment of the pr...
TL;DR: Various methods used in purifying F. buski hemoglobin are described and some of its chemical and physical properties are reported.
Abstract: Hemoglobin was purified by gel filtration, ion exchange chromatography, and preparative disc electrophoresis, using ammonium sulfate fractions of homogenized worms; the last method yielded the best results. A molecular weight of 15,000 to 17,500 was determined by gel filtration, SDS-acrylamide electrophoresis, sedimentation equilibrium and amino acid composition. The protein resembles vertebrate myoglobin in lacking subunits, having one heme, and containing a similar number of amino acids, but half cystine and taurine were detected in preparations of the parasite hemoglobin. Absorption spectra and extinction coefficients were determined for the purified hemoglobin and its derivatives. In a notable review, Lee and Smith (1965) cited the lack of information on the hemoglobins of trematodes. Since then, Lutz and Siddiqi (1967) have investigated the hemoglobin of Fasciola gigantica using electrophoresis and spectrophotometry. More recently, Fasciolopsis buski, the intestinal fluke of man and pigs, was found to contain large amounts of hemoglobin (Cain, 1969a). The pigment was among the three most abundant soluble proteins in homogenates analyzed by disc electrophoresis, and its electrophoretic mobility at pH 8.3 closely resembled that of pig myoglobin. Subsequent studies (Cain, 1969b) revealed that F. buski is capable of synthesizing the protein portion of its hemoglobin, but the source of heme was not clearly determined. The present paper describes various methods used in purifying F. buski hemoglobin and reports some of its chemical and physical properties. MATERIALS AND METHODS
TL;DR: The procedure of preparation includes fractionation of the extracted proteins by heat treatment and Sephadex chromatography for a complete separation of myoglobin from hemoglobin, and pure metmyoglobin can be obtained by lyophilisation.