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Biomedical subjects

N C Price

Publications and source records attributed to N C Price.

At least 109 records · Page 6Linked to original sources
PubMed1991

The unfolding and refolding of pig heart fumarase.

The unfolding of pig heart fumarase in solutions of guanidinium chloride (GdnHCl) has been examined. Loss of activity occurs at lower concentrations of GdnHCl than the structural changes detected by fluorescence or c.d. After denaturation, regain of activity can be observed provided that a reducing agent (dithiothreitol) is present and that the concentration of GdnHCl is lowered by dialysis rather than by dilution. The regain of secondary structure occurs with high efficiency even when little or no activity is recovered.

Animals↗
PubMed1991

Solution structures of calcitonin-gene-related-peptide analogues of calcitonin-gene-related peptide and amylin.

Near-u.v. and far-u.v. c.d. spectra of human alpha-calcitonin-gene-related peptide (h alpha CGRP), analogues and fragments of CGRP and amylin were recorded in aqueous solution and in trifluoroethanol (TFE)/water mixtures. All peptides contained significant amounts of alpha-helix in aqueous solution, and this amount increased on adding TFE. The helical content was unaffected by pH and salt. However, amylin contained much less helix than CGRP and the c.d. spectrum was more temperature-sensitive. A band in the near-u.v. c.d. spectrum of CGRP (but not present in the spectrum of amylin) was attributed to the disulphide bond in CGRP. The intensity of this band was pH-dependent and titrated with a pKa of 6.5, suggesting the involvement of histidine ionization.

Amino Acid Sequence↗
PubMed1991

Selective modification by transglutaminase of a glutamine side chain in the hinge region of the histidine-388----glutamine mutant of yeast phosphoglycerate kinase.

The transglutaminase-catalysed incorporation of putrescine and monodansylcadaverine into yeast phosphoglycerate kinase has been studied. There is little incorporation of the amines into wild-type enzyme, but nearly stoichiometric incorporation into the histidine-388----glutamine mutant enzyme. C.d. studies show that the overall structure of the mutant enzyme is very similar to that of the wild-type enzyme. Incorporation of the amines into the mutant enzyme causes no significant change in its activity. Glutamine-388 was shown, by isolation and sequencing of the modified peptide, to be the site of incorporation of monodansylcadaverine into the mutant enzyme. The specificity of the transglutaminase reaction is discussed in the light of available data.

Amino Acid Sequence↗
PubMed1991

A comparative study of the structure of egg-white riboflavin binding protein from the domestic fowl and Japanese quail.

1. The riboflavin binding proteins from domestic fowl and Japanese quail have been isolated and their structures compared by circular dichroism, fluorescence and peptide mapping. 2. The two proteins have similar secondary structures, but differ in their tertiary structures as reflected in the environments of aromatic amino acid side chains. 3. Differences in amino acid sequence between the proteins are indicated by the digestion patterns obtained with thermolysin, chymotrypsin and V8 proteinase from Staphylococcus aureus. Both proteins are resistant to digestion by trypsin.

Animals↗
PubMed1991

Secondary structures of narcissus mosaic virus coat protein.

Circular dichroism (CD) measurements on the coat protein of narcissus mosaic virus particles show that the dominant secondary structure is the alpha-helix, with a 45 (+/- 2)% content. The beta-sheet content is much lower at 5 (+/- 3)%. Both values are essentially the same as those found in potato virus X coat protein. The CD results are used to assess the results of secondary structure prediction methods.

Capsid↗
PubMed1990

The unfolding and attempted refolding of citrate synthase from pig heart.

The unfolding of the dimeric enzyme citrate synthase from pig heart in solutions of guanidinium chloride (GdnHCl) was studied. Data from fluorescence, circular dichroism (CD) and thiol group reactivity studies indicated that the enzyme was almost completely unfolded at GdnHCl concentrations greater than or equal to 4 M. On dilution of GdnHCl, essentially no reactivation of the enzyme occurred. The implications of this finding for the process of folding and assembly in vivo of this and other mitochondrial enzymes are discussed. Exposure of the enzyme to high pH (9-10) led to only a small loss of secondary structure and partial reactivation could be observed on readjustment of the pH to 8.0.

Animals↗
PubMed1990

The unfolding and attempted refolding of mitochondrial aspartate aminotransferase from pig heart.

The unfolding of the mitochondrial isoenzyme of aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) has been studied. By a number of criteria (enzyme activity, protein fluorescence, c.d., thiol-group reactivity), the enzyme was judged to be almost completely unfolded in 2 M-GdnHCl. On dilution of the GdnHCl, no re-activation of the enzyme could be observed, whether or not pyridoxal 5'-phosphate and dithiothreitol were present. The behaviour of the mitochondrial isoenzyme is in marked contrast with that of the cytoplasmic isoenzyme [West & Price (1989) Biochem. J. 261, 189-196], despite the similarities in the amino acid sequences and tertiary structures of the two isoenzymes. The implications of these findings for the process of folding and assembly of the mitochondrial isoenzyme in vivo are discussed.

Animals↗
PubMed1989

The unfolding and refolding of cytoplasmic aspartate aminotransferase from pig heart.

The unfolding of cytoplasmic aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) was studied. Data from protein fluorescence, c.d. and thiol-group reactivity indicated that the enzyme was unfolded in 6 M-GdnHCl. Spectroscopic studies showed that this unfolding was accompanied by dissociation of the pyridoxal 5'-phosphate cofactor. On dilution of the GdnHCl, re-activation of the enzyme occurred in reasonable yield, provided that dithiothreitol and pyridoxal 5'-phosphate were present. The regain of activity obeyed second-order kinetics. In the absence of added dithiothreitol and pyridoxal 5'-phosphate, substantial formation of high-Mr aggregates occurred.

Adenosine Diphosphate↗
PubMed1989

Intraocular nocardiosis: a further case and review.

A case is presented of bilateral intraocular nocardial infection associated with lung and liver foci and responding to treatment. Difficulties in diagnosis and treatment are discussed. It is suggested that unusual infections such as this should be considered in the differential diagnosis of chorioretinitis, and should be carefully sought, especially in immunocompromised patients. However, our patient is unusual in having no evidence of immunosuppression predisposing to ocular involvement in his nocardial infection.

Biopsy↗
PubMed1988

Do metal ions promote the re-activation of the 2,3-bisphosphoglycerate-independent phosphoglycerate mutases?

It has been reported [Smith, McWilliams & Hass (1986) Biochem. Biophys. Res. Commun. 136, 336-340] that addition of certain metal ions, notably Co2+ and Mn2+, promoted the refolding of denatured phosphoglycerate mutase from wheat germ. We have re-investigated these experiments and have shown that, when precautions are taken to avoid artefacts in the assay system, the metal ions do not promote any re-activation of the denatured wheat-germ or Aspergillus nidulans enzymes. An alternative explanation is offered for the observations of Smith et al. (1986).

2,3-Diphosphoglycerate↗
PubMed1988

The unfolding and refolding of glutamate dehydrogenases from bovine liver, baker's yeast and Clostridium symbosium.

The unfolding behaviour of the hexameric glutamate dehydrogenases from bovine liver, Clostridium symbosium and baker's yeast in solutions of guanidinium chloride (GdnHCl) was studied. Changes in Mr studied by light-scattering indicate that, in each case, the hexamer dissociates to form trimers, which then dissociate to monomers at higher concentrations of GdnHCl. Dissociation to trimers is accompanied by a reversible loss of enzyme activity, but no gross structural changes can be detected by fluorescence or c.d. Dissociation to monomers is accompanied by large structural changes, and the loss of activity cannot be reversed by dilution. The parallel behaviour of all three enzymes shows that the previously noted inability of the isolated subunits of the bovine liver enzyme to refold [Bell & Bell (1984) Biochem. J. 217, 327-330] is not a result of any modification of the enzyme as a result of import into mitochondria, since the C. symbosium and baker's-yeast enzymes do not undergo any such post-translational translocation.

Animals↗
PubMed1987

Denaturation and renaturation of the monomeric phosphoglycerate mutase from Schizosaccharomyces pombe.

The denaturation by guanidinium chloride of the monomeric phosphoglycerate mutase from Schizosaccharomyces pombe was studied. The loss in activity broadly parallels the changes in protein structure detected by fluorescence and c.d. Renaturation can be brought about by dilution of the denaturing agent. These processes were compared with those in the enzymes from baker's yeast and rabbit muscle, which are tetrameric and dimeric respectively. The effects of the cofactor 2,3-bisphosphoglycerate on the structure and stability of the S. pombe enzyme were also investigated.

Circular Dichroism↗
PubMed1987

The diagnosis and surgical management of acquired bilateral superior oblique palsy.

Thirty-four patients with surgically treated bilateral superior oblique palsy are presented. The patients are divided into three groups: Symmetrical palsies, Asymmetrical palsies, A group in whom the bilaterality was initially masked. Bilaterality should be suspected in all cases of traumatic IVth nerve paresis, and particularly in cases with a large 'V' pattern, excyclo deviation of more than 10 degrees on down-gaze and when right hypertropia switches to left hypertropia on lateral down-gaze. Bilateral Harada-Ito procedures alone 'cured' 11 of 17 patients (65 per cent) in groups 1 and 2, and is the operation of choice in acute bilateral superior oblique palsy. Cyclo deviation was reduced by a mean of 5.5 degrees in the primary position and by 6-10 degrees in down-gaze. Patients initially managed with other surgery had a more complicated surgical course and required more operations. Seven patients who initially demonstrated only gross fusion recovered good fusion after Harada-Ito surgery.

Adolescent↗
PubMed1987

The correction of post-keratoplasty astigmatism.

The results of refractive surgery for post-keratoplasty astigmatism in 41 eyes are presented. Thirty-nine eyes regained a functional vision of 6/12 or better. Relieving incisions and compression sutures are the most useful procedures, but more than one operation may be required.

Adolescent↗
PubMed1987

Congenital horizontal tarsal kink: a simple surgical correction.

A case is reported in which a simple anterior lamellar repositioning procedure was used successfully to repair an upper lid entropion associated with a horizontal tarsal kink. This obviates the need for the more complex and destructive procedures which have previously been described for the treatment of this condition.

Entropion↗