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G R Moore

Publications and source records attributed to G R Moore.

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

NMR study of the structural characteristics of variants of yeast iso-1-cytochrome c in which unvaried aromatic residues have been substituted.

The structures of variants of yeast iso-1-cytochrome c, in which the previously unchanged Tyr48 and Tyr48 + Trp59 have been replaced by Phe, have been characterised by NMR. The NMR data indicated that the structures of the variant cytochromes c are very similar to the wild-type protein. In particular, the heme environment and interactions of the heme macrocycle were shown to be preserved. The observation of chemical shift differences have allowed for the assessment of conformational changes. The substitution of Trp59 by Phe may have caused a small conformational change, a manifestation of which is the observed chemical shift differences at His39, Val57 and Tyr74. The structural basis for the reduction in redox potential accompanying the amino acid substitutions is discussed and the proposal made that the changes in potential are a direct consequence of the side chain properties and do not result primarily from conformational changes.

Amino Acids↗
PubMed1991

Aluminium transport in blood serum. Binding of aluminium by human transferrin in the presence of human albumin and citrate.

The binding of Al3+ by human serum transferrin has been investigated by u.v.-visible difference spectroscopy. In the presence of 25 mM-HCO3- at pH 7.4, the apparent association constants were found to be 1.69 x 10(12) M-1 and 5.36 x 10(11) M-1. These association constants are pH-dependent, reducing with both increasing and decreasing pH. The apparent pKa values were found to be 6.7 and 8.2. Competitive assays of binding of Al3+ to transferrin in the presence of citrate and human serum albumin at molar ratios corresponding to those found in normal plasma showed that a considerable amount of Al3+ was not bound to transferrin. Taking a concentration of 5 microM as a typical value observed for the plasma of patients on haemodialysis [Harris & Sheldon (1990) Inorg. Chem. 29, 119-124] the competitive binding assay indicate that approximately 60% of it is bound to transferrin, approximately 34% to albumin and the remainder to citrate. These results therefore suggest that, although transferrin at pH 7.4 is the major Al(3+)-binding component of plasma, an appreciable amount of Al3+ present in patients on haemodialysis may be bound to albumin.

Aluminum↗
PubMed1991

Electron transfer between horse ferritin and ferrihaemoproteins.

Reactions of reduced horse spleen ferritin with horse and Saccharomyces cerevisiae ferricytochromes c, cow ferricytochrome b5, sperm-whale metmyoglobin and Pseudomonas aeruginosa ferricytochrome c-551 were investigated by u.v.-visible spectrophotometry. In all cases the reduced ferritin reduced the ferrihaemoproteins. The rate of reduction varied from less than 0.2 M-1.s-1 for metmyoglobin to 1.1 x 10(3) M-1.s-1 for horse ferricytochrome c (0.1 M-phosphate buffer, pH 7.4, at 25 degrees C). We conclude that the mechanism of ferrihaemoprotein reduction involves long-range electron transfer through the coat of ferritin and that such electron transfer is rapid enough to account for the rates of iron release observed by other workers in reductive release assays.

Animals↗
PubMed1991

Change in charge of an unvaried heme contact residue does not cause a major change of conformation in cytochrome c.

The structure of the Ala38 variant of yeast iso-1-cytochrome c, in which the previously unchanged Arg38 has been replaced, has been characterised by NMR. The NMR data indicate that the structure of the Ala38 variant is very similar to that of the wild type protein. In particular, the heme environment and interactions of the heme macrocycle are shown to be preserved. Analysis of the chemical shift perturbations to the resonances of Ile35 is shown to be consistent with the change in charge at position 38. The only significant area of conformational change detected was at residues 39 and 58, close to the site of modification. Therefore the redox potential change accompanying the modification [1988, Biochemistry 28, 3188-3197] appears to be a direct consequence of the altered side-chain of residue 38 and not a result of secondary conformational changes induced by the modification.

Alanine↗
PubMed1991

Bacterial 4-alpha-helical bundle cytochromes.

The biological functions of cytochrome c' and bacterioferritin, both haemoproteins with a common 4-alpha-helical bundle structure, are discussed and an example given of one of Kamen's laws, namely: comparative studies of prokaryotic cytochromes and their eukaryotic counterparts are useful. In the present case, the comparison is between bacterioferritin and its animal counterpart, haemoferritin.

Animals↗
PubMed1991

Mössbauer spectroscopic studies of iron in Pseudomonas aeruginosa.

The present Mössbauer spectroscopic studies of isolated bacterioferritin and whole cells of Pseudomonas aeruginosa have shown that the iron core of bacterioferritin is not altered on isolation. These studies have also shown that the bacterioferritin core is typically 85% oxidized within the cell and may contain a significant proportion of its iron as small clusters during the early stage of the stationary phase of cell growth.

Bacterial Proteins↗
PubMed1991

The effect of tea on iron and aluminium metabolism in the rat.

Weanling male Wistar rats were fed for 28 d on a semi-synthetic diet containing normal (38 micrograms/g) or low (9 micrograms/g) levels of iron. They were given water or tea infusion (20 g leaves/l water) to drink. Two further groups were given a normal- or low-Fe diet containing added tea leaves (20 g/kg diet). At the end of the study period, all rats given the low-Fe diet were severely anaemic, as assessed by haemoglobin, packed cell volume and liver Fe. Those given tea or the diet with added tea leaves showed a greater degree of Fe depletion. The blood and liver aluminium levels were not increased as a result of consuming tea or tea leaves, despite the higher Al intakes. Fe deficiency per se had no effect on Al absorption or retention from tea. It was concluded that the Al in tea was very poorly absorbed but that tea, either in the form of an infusion or as tea leaves, had an adverse effect on Fe status.

Aluminum↗
PubMed1990

Haem binding to horse spleen ferritin.

Horse spleen ferritin, a spherical protein shell of 24 subunits, contains no haem when extracted. This contrasts with ferritins isolated from bacterial sources which have the capacity to bind up to 24 haem groups [(1990) FEBS Lett. 271, 141-143] via two methionine residues [(1990) Nature 341, 771]. Here it is shown that horse spleen ferritin can bind between 15 and 17 haems per 24 subunits with an apparent association constant of 2.2-3.2 x 10(4) M-1. The strength of haem binding appears to be unaffected either by the presence of the core or by the oxidation state of the haem. The demonstration of the ability of animal ferritin to bind haem strengthens the similarity between it and bacterioferritin and could have major consequences for its mechanism of action in physiological iron uptake and release processes.

Animals↗
PubMed1990

Bacterial ferritin contains 24 haem groups.

Pseudomonas aeruginosa bacterioferritin, also known as cytochrome b1 or cytochrome b557, has been isolated with 9 haems per 24 subunits. Various forms of the protein have been prepared including the completely haem-free protein and the fully haem-loaded protein with 24 haems per 24 subunits. The presence of the core does not significantly affect haem addition or removal. The absorbance ratio of the non-haem-iron-loaded protein, 278 nm:417 nm (oxidised), can be used to estimate the haem loading.

Bacterial Proteins↗
PubMed1990

Bis-methionine axial ligation of haem in bacterioferritin from Pseudomonas aeruginosa.

The iron-containing bacterioferritins contain the protoporphyrin IX haem group. It has been established that Escherichia coli cytochrome b1, cytochrome b557 and bacterioferritin are identical. The optical spectra at room temperature of the haem group show it to be predominantly low-spin in both the ferrous and ferric states. The nature of the axial ligands binding the haem group to the polypeptide has, however, remained unknown. Low-spin, bis-coordinate haem centres in proteins typically have a role in rapid electron transfer as redox changes at the metal ion lead to little structural rearrangement. There are only four amino acids with side-chains that have ligand field strengths sufficient to generate the low-spin state of haem, namely, histidine, lysine, methionine and cysteine. Hence there are, potentially, ten different pairs of these four ligands which could be discovered in electron transfer haemoproteins. To date only three have been established with certainty. They are bis-histidine, as in mammalian cytochrome b5, methionine-histidine, typified by cytochrome c and lysine-histidine, recently recognized by spectroscopic methods in cytochrome f. Here we report the electron paramagnetic resonance and near infrared magnetic circular dichroism spectra of the oxidized state of Ps. aeruginosa bacterioferritin which enable the axial ligands to be identified as the thioether side chains of two methionine residues, a ligation scheme not previously reported for haem in any protein.

Bacterial Proteins↗
PubMed1990

NMR characterization of surface interactions in the cytochrome b5-cytochrome c complex.

The complex formed in solution by native and chemically modified cytochrome c with cytochrome b5 has been studied by 1H and 13C nuclear magnetic resonance spectroscopy (NMR). Contrary to predictions of recent theoretical analysis, 1H NMR spectroscopy indicates that there is no major movement of cytochrome c residue Phe82 on binding to cytochrome b5. The greater resolution provided by 13C NMR spectroscopy permits detection of small perturbations in the environments of cytochrome c residues Ile75 and Ile85 on binding with cytochrome b5, a result that is in agreement with earlier model-building experiments. As individual cytochrome c lysyl residues are resolved in the 1H NMR spectrum of N-acetimidylated cytochrome c, the interaction of this modified protein with cytochrome b5 has been studied to evaluate the number of cytochrome c lysyl residues involved in binding to cytochrome b5. The results of this experiment indicate that at least six lysyl residues are involved, two more than predicted by static model building, which indicates that cytochrome c and cytochrome b5 form two or more structurally similar 1:1 complexes in solution.

Carbon Isotopes↗
PubMed1990

Multiple sclerosis: a role for astroglia in active demyelination suggested by class II MHC expression and ultrastructural study.

Central nervous system (CNS) tissue was studied by immunocytochemistry and electron microscopy from three cases of multiple sclerosis (MS) in which evidence of ongoing myelin breakdown could be documented. The study focussed upon the role of glial cells in the pathogenesis of demyelination. In acute MS, demyelination involved the vesicular dissolution of myelin from intact axons and a paucity of fibrillary astrogliosis. Foamy macrophages, many of them probably derived from transformed and recently proliferated microglia, contained recognizable myelin debris and lipid droplets and were abundant throughout the lesions. These cells formed the major phagocytic population and stained positively for class II major histocompatibility complex antigens (HLA-DR; Ia). In acute MS lesions, rounded astrocytes were encountered which possessed membrane-bound compartments enclosing phagocytosed fragments of myelin basic protein-positive debris. Despite the superficial resemblance of these cells to foamy macrophages, the presence of intermediate filaments, glycogen granules and diffuse glial fibrillary acidic protein positivity supported an astroglial identity. Astrocyte processes were involved in myelin removal and invested recently demyelinated axons. Hypertrophic fibrous astrocytes were common in chronic active lesions, were capable of myelin degradation and on occasion, contained myelin debris attached to clathrin-coated pits. These astrocytes were sometimes Ia+. Oligodendrocytes were depleted from the center of active lesions but were numerous at the lesion margin, suggesting survival and proliferation. They stained positively for myelin-associated glycoprotein, a marker for immature oligodendrocytes. However, they were invariably Ia-. The findings confirm and further support a role for the astrocyte as both an antigen presenting cell and a phagocyte in the CNS during MS.

Adolescent↗
PubMed1989

A 1H NMR study of bovine cytochrome oxidase. Paramagnetically shifted resonances of haem a.

Dimeric and monomeric forms of mitochondrial cytochrome oxidase (EC 1.9.3.1) have been examined using 1H NMR spectroscopy. Paramagnetically shifted resonances were detected in spectra of the monomeric protein. Studies of this protein in a number of oxidation and ligation states have assigned these resonances to ferrihaem a. The temperature and pH dependence of this new probe of haem a environment is reported.

Animals↗
PubMed1989

Role of arginine-38 in regulation of the cytochrome c oxidation-reduction equilibrium.

Arg-38 is an internal residue of mitochondrial cytochrome c that is close to heme propionate-7. Previous work comparing the behavior of cytochromes c from several species [Moore, G. R., Harris, D. E., Leitch, F. A., & Pettigrew, G. W. (1984) Biochim. Biophys. Acta 764, 331-342] has suggested that Arg-38 lowers the pKa of this propionate group and thereby accounts for the relative pH independence of the cytochrome c reduction potential from pH 5 to pH 8. The influence of Arg-38 on the oxidation-reduction equilibrium of yeast iso-1-cytochrome c has now been investigated by electrochemical, NMR, and theoretical analysis of six specifically mutated forms of this protein in which Arg has been replaced by Lys, His, Gln, Asn, Leu, or Ala. As the electron-withdrawing character of the residue at position 38 decreases, the reduction potential of the protein also decreases, with the largest decrease (ca. 50 mV) observed for the Ala variant. However, the variation in the reduction potentials of the mutants as a function of pH was similar to that observed for the wild-type protein. The effects of some of these mutations on the pKa values of His-33 and His-39 have been determined by NMR spectroscopy and found to be minimal. Calculations of the electrostatic free energy for the Leu-38 variant predict a decrease in the reduction potential of this mutant that is remarkably close to that observed experimentally. This work establishes that while Arg-38 contributes to the relatively high reduction potential of cytochrome c, this residue does not appear to be the sole functionality responsible for lowering the heme propionate-7 pKa.

Amino Acids↗
PubMed1989

A denaturation-induced proton-uptake study of horse ferricytochrome c.

The observation that 6 M-urea denatures horse ferricytochrome c in the pH range 4-6, but not horse ferrocytochrome c, has been exploited to determine the denaturation-induced proton uptake of ferricytochrome c. This is related to the pKa values of ionizable groups buried within the native protein. The data indicate that one of the haem propionic acid substituents of ferricytochrome c has a pKa of less than 4.5, whereas the other has a pKa of greater than 9.

Amino Acids↗
PubMed1989

Fourier-transform infra-red studies of the alkaline isomerization of mitochondrial cytochrome c and the ionization of carboxylic acids.

The alkaline transitions of tuna and horse ferricytochromes c and the trifluoroacetyl-lysine derivative of horse ferricytochrome c have been studied by Fourier-transform (FT) i.r. spectroscopy. The spectral perturbations resulting from the transition have been interpreted by reference to FT i.r. data on simple carboxylic-acid-containing compounds and a bacterial cytochrome c551 in which a haem propionate ionizes without causing a significant conformational change. The analysis strongly suggests that ionization of a haem propionate of mitochondrial cytochrome c triggers the alkaline conformation change.

Animals↗
PubMed1989

Tropical spastic paraparesis: a model of virus-induced, cytotoxic T-cell-mediated demyelination?

Tropical spastic paraparesis is a neurological disorder that is most commonly seen in certain tropical (mainly Caribbean) areas and that presents as a progressive spastic paraparesis and urinary dysfunction. Recent studies have revealed an association between tropical spastic paraparesis and human T-cell lymphotropic virus type I (HTLV-I) infection. We report the results of a detailed morphological and immunocytochemical study of a patient with tropical spastic paraparesis. Lesions were restricted to the spinal cord and optic nerve, where demyelination, inflammation, and fiber loss were common features. Lymphocytes were seen closely applied to nerve fibers within which were changes resembling those seen in myelinated central nervous system cultures exposed to cytokines. Immunocytochemically, HTLV-I p19 core protein and a predominance of CD8+ (suppressor/cytotoxic) T cells and expression of class I major histocompatibility antigen were demonstrated in spinal cord lesions. It is postulated that cytotoxic T cells, either directly or via cytokines, induce lysis of the myelin sheath and subsequently the axon, resulting in a mixed picture of demyelination and axonal loss with secondary tractal degeneration. Despite this destruction, extensive remyelination was evident within affected areas of spinal cord.

Female↗