PubMed Health⌕ Search

Biomedical subjects

A M Foote

Publications and source records attributed to A M Foote.

8 recordsLinked to original sources
PubMed1985

Physical studies by NMR and circular dichroism determining three structurally different domains in Physarum polycephalum histone H1.

Combined studies which include, NMR spectroscopy, circular dichroism, amino acid analysis and polyacrylamide gel electrophoresis together show that the protein designated as histone H1 from Physarum polycephalum has many of the features of histone H1 derived from other sources. The molecular masses of the globular peptide and the whole molecule were found to be 9000 +/- 1000 Da and 33000 +/- 3000 Da respectively. NMR melting experiments showed that the half-melt temperature was 53 +/- 1 degree C and the enthalpy of melting was 100 kJ . mol-1. Unusual facets of the molecule are the relatively large numbers of histidine residues (6 or 7) and the mono, di and trimethylation of some of the lysines, the major type of modification being trimethylation of 9 +/- 2 residues. The conditions necessary for structuring Physarum H1 are not the same as the histone H1 from calf thymus. It is suggested that titration of the histidine residues is the most decisive step for the development of tertiary folding of the globular unit.

Amino Acids↗
PubMed1983

Stopped-flow solution scattering using synchrotron radiation: apparatus, data collection and data analysis.

We have constructed an experimental system, under remote control, for stopped-flow X-ray scattering using synchrotron radiation. It has been used, in conjunction with an annular detector and its associated electronics, to obtain good scattering curves, with time-slices as short as 200 ms, in a new study of the dissociation of the enzyme complex aspartate transcarbamylase. The data have been analysed by new statistical methods, and they agree well with the results from parallel chemical quench experiments. For studying dissociation reactions, stopped-flow X-ray scattering is a quite practical method, which need not use very much more material than conventional stopped-flow experiments.

Aspartate Carbamoyltransferase↗
PubMed1982

Zinc-sulfur bonds of aspartate transcarbamylase studied by x-ray absorption spectroscopy.

X-ray absorption spectra have been recorded for aspartate transcarbamylase [unligated and ligated with the transition-state analogue N-(phosphonoacetyl)-L-aspartate] and for the model compound zinc dimethyldithiocarbamate. The spectra confirm that, in the enzyme, the zinc atom is ligated to four sulfur atoms, with a mean distance of 2.34 +/- 0.03 A. A spread in bond lengths of 0.1 +/- 0.03 A is possible, due to thermal and/or static disorder. No significant difference was found between the spectra of the ligated and unligated enzymes.

Aspartate Carbamoyltransferase↗
PubMed1980

Stopped-flow x-ray scattering: the dissociation of aspartate transcarbamylase.

A combination of stopped-flow and x-ray scattering techniques was used to study the dissociation of aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) with a 2:1 excess of p-chloromercuribenzenesulfonic acid (the ratio being calculated on a basis of reactive sites), in the presence and absence of the transition state analogue N-(phosphonacetyl)-L-aspartate. At 10 mg of protein per ml, the scattering curves allowed some details of the reaction to be followed with a time resolution down to 1 sec. The curves showed not only the dissociation of the enzyme complex but also the formation of the subunits. These results show that, with present facilities, x-ray scattering could be used to study dissociation or reassociation reactions with a time resolution of the order of 100 msec.

Allosteric Regulation↗
PubMedDate not supplied

Expression of the preproenkephalin A gene in tumor cells and brain glioma: a northern and in situ hybridization study.

Preproenkephalin A (PPA) mRNA expression was studied by Northern blot and in situ hybridization in cell lines (rat glioma C6, rat hepatoma HTC, human neuroblastoma IMR32, mouse neuroblastoma NS20Y, rat fibroblast FR3T3, human bladder carcinoma EJ, human vulva carcinoma A431, myelocytic leukemia HL60, rat adrenal carcinoma Y1) and in brain tumours (implanted C6 cells). C6 glioma in cell culture, as well as in brain tumours, expressed high levels of PPA mRNA as compared to the caudate nucleus of the rat brain. EJ and FR3T3 cell lines also expressed the PPA mRNA, which was not detectable in A431, Y1, NS20Y, IMR32, HTC, HL60 cell lines as well as in the rat liver. This observation provides an interesting model to study the mechanisms by which the malignant transformation can induce in glial cells the derepression of a gene which is usually expressed in neurons or in neuron-like cells.

Animals↗
PubMedDate not supplied

Amplification of oncogenes in lung carcinoma grafted in nude mice.

Seven lung carcinomas were grafted on nude mice and continuously propagated as in vivo models on which the amplification of 9 oncogenes (N-myc, v-erb A, v-abl, v-sis, c-myc, c-myb, v-Ha-ras, c-Kiras, and v-scr) was studied by Southern blot hybridization. Only c-myc was amplified (20 copies) in an adenocarcinoma. The presence of 2 bands at 9 kb and 6.6 kb in addition to the normal 12.7 kb in EcoR1 digested DNAs suggested a polymorphism of the c-myc gene in this tumor. The other 8 oncogenes were not amplified in this tumor. The 5 small cell lung carcinomas of this study did not show any amplification of any of the 9 oncogenes tested.

Adenocarcinoma↗