Search PubMed⌕ Search

Biomedical subjects

M Zama

Publications and source records attributed to M Zama.

16 recordsLinked to original sources
PubMed1992

New case of Bartsocas-Papas syndrome surviving at 20 months.

We report on patient with Bartsocas-Papas syndrome surviving at age 20 months. Similar to 7 previously reported families, this patient is of Mediterranean ancestry, pointing to clustering of the responsible mutant gene in Southern Europe. In 3 of the 11 Bartsocas-Papas syndrome patients described so far, including the present case, the condition has not been neonatally lethal. This suggests that about one-fourth of these patients could survive. This information is important for genetic counseling.

Abnormalities, Multiple↗
PubMed1991

Arginine residues involved in strong histone--DNA interactions to fold DNA into the nucleosome core particle.

The numbers of the arginine residues involved in strong histone-DNA interactions to fold DNA into a nucleosome core particle were determined for each of the four core histones, by kinetic studies of chemical modification of the residues in the nucleosome core particle. It was suggested that the arginines in the globular region of H3 histone make major contributions to the strong binding of the octameric histones to the core DNA.

Animals↗
PubMed1990

Codon usage pattern in alpha 2(I) chain domain of chicken type I collagen and its implications for the secondary structure of the mRNA and the synthesis pauses of the collagen.

A stability map of local secondary structure of the mRNA of the triple-helical alpha 2(I) chain domain of chicken type I collagen was obtained by plotting the free energy of the optimal secondary structure of a local segment in mRNA against the segment position along a base sequence of the mRNA. It was found that the positions of the minima of free energy in the plot coincide with the positions where synthesis pauses of the alpha-chain polypeptides of the corresponding sizes translated from the mRNA have been reported to occur (1). The codon usage pattern of each of the three major amino acids of the alpha-chain domain of the collagen, Gly, Pro and Ala, fluctuates considerably along the base sequence segments of the mRNA and a deviation of the pattern from that of the average of the whole alpha 2(I) chain domain mRNA, particularly for Gly codons, leads to a loss of the stability of the local secondary structure of the mRNA. The results suggest that selection has operated on the codon usage to optimize the secondary structure characteristic of the mRNA of the chicken collagen alpha 2(I) chain domain which leads to a nonuniform polypeptide elongation pattern.

Animals↗
PubMed1990

Codon usage and secondary structure of mRNA.

The specific codon usage pattern of the repetitive unit nucleotide sequence of silk fibroin mRNA suggests that selection has operated on the codon usage to optimize the secondary structure characteristic of the mRNA. The correlation between the stability map of local secondary structure of type I collagen mRNA and the codon usage pattern and the translation rate of the collagen is also implied.

Animals↗
PubMed1988

Specific codon usage pattern and its implications on the secondary structure of silk fibroin mRNA.

We have identified two distinctive regions of the repetitive unit nucleotide sequence of fibroin mRNA of Bombyx mori. The codon usage for the major amino acids, glycine, alanine and serine is distinctly different in these two regions, indicating that it is determined by the fibroin mRNA or gene structure but not by the tRNA population. Comparative computer analyses of nucleotide substitutions in the unit sequence suggest that selection has operated on the codon usage to optimize the secondary structure characteristic of the fibroin mRNA.

Amino Acid Sequence↗
PubMed1988

Interparticle interactions and structural changes of nucleosome core particles in low-salt solution.

The structural behavior of the nucleosome core particles in the range of solvent Na+ concentration from 10.45 to 0.45 mM has been studied by small-angle neutron and synchroton radiation X-ray scattering, sedimentation, atomic absorption spectroscopy, density measurements, and circular dichroism. With decreasing salt concentration, the appearance of a scattering peak that is assignable to interparticle interactions, an intraparticle structural transition, a decrease in the sedimentation velocity of the particle, and a release of bound Na+ ions from the particle are all observed concurrently when the ratio of solvent Na+ ions per particle is below approximately 1000. These observations are interpreted to indicate that a release of bound Na+ ions from the particle brings about structural rearrangements and weakens the electrostatic shielding of the particle, and this introduces long-range repulsive ordering of the particle in low-salt solution. Analyses of the scattering data indicate that the rearrangement within the core particle in low-salt solution is slight, changing the particle's shape slightly from cylindrical to a more spherical form by moving the center of the mass of the DNA somewhat inward with accompanying small decreases in the radii of gyration of both the DNA and the histones.

Animals↗
PubMed1985

Distinction and similarity in the structure of histones H1 and H5 as indicated by 13C nuclear-magnetic-resonance spectroscopy.

The 13C nuclear magnetic resonance studies have been carried out on histones H1 and H5, by focusing our interest on possible formation of specific salt bridges between acidic and basic amino acid residues in the proteins and also on the structural difference between the two proteins. The 13C chemical shift and pKa values of the carboxyl group of glutamic acid residues in the histones coincided with those of free glutamic acid. Based on this result and another experiment using completely modified lysine residues in the histones, no evidence for a specific interaction between acidic and basic residues has been found. It has also been shown that the pH-effects of aliphatic and aromatic resonances are quite different between H1 and H5, suggesting that the globular domain of H5 is more stable than that of H1. The correlation time (1.5 ns) for the alpha-carbons of H5 estimated from 13C nuclear Overhauser enhancement was twice as long as that of H1 (0.9 ns), indicating that the backbone in the N-terminal and C-terminal domains of H5 is less mobile than that of H1.

Arginine↗
PubMed1978

Nucleosome conformation: pH and organic solvent effects.

Monomer nucleosomes (nu 1) from chicken erythrocyte nuclei were examined in aqueous buffers (8 greater than pH greater than 3) and in solvent mixtures (i.e., water and ethanol, ethylene glycol, dioxane, dimethyl sulfoxide, 2-methyl-2,4-pentanediol, polyethylene glycol, sucrose, or urea). Circular dichroism, laser Raman spectroscopy of nu 1, and the fluorescence of nu 1 labeled with N-(3-pyrene) maleimide on thiol groups of H3 histone were employed to detect conformational transitions in nu 1. The results of pH studies were as follows: 5.5 greater than pH greater than 4.8, suppression of DNA ellipticity and no change of histone alpha-helix; 4.6 greater than pH greater than 4.2 an irreversible increase in the B character of DNA, a slight loss of histone alpha-helix, and a parallel loss of pyrene excimer fluorescence; 4 greater than pH, aggregation of nu 1 and protonation of the DNA bases C and A. Results obtained in the studies of nu 1 in solvent mixtures included the following: sharp conformational transitions that variously involved an increase in the B character of DNA, a slight loss of histone alpha-helix, and a loss of pyrene excimer. Different solvents required different concentrations to effect these conformational changes.

Alcohols↗
PubMed1976

Structure of wye (Yt base) and wyosine (Yt) from Torulopsis utilis phenylalanine transfer ribonucleic acid.

A fluorescent base wye (Yt base) was isolated from Torulopsis utilis tRNAPhe. The structure was established as 4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazo[1,2-alpha]purine based on ultraviolet (uv), nuclear magnetic resonance (NMR), and mass spectra, and by direct comparison with synthetic material. The nucleoside, wyosine (Yt), was isolated from purified tRNAPhe by enzymatic degradations followed by column and thin-layer chromatographies. The structure of wyosine is proposed as 3-ribofuranosyl-4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazol[1,2-alpha]purine (the ribosyl group is attached to the N-9 position of guanine nucleus) on the basis of comparison with model compounds.

Candida↗
PubMed1975

Different effects of polylysine and polyarginine on the transition to a condensed state of DNA in polyethyleneglycol/salt solution.

Circular dichroism spectroscopy has been used to investigate the influence of polylysine and polyarginine on the transition to a condensed state of DNA brought about by high concentrations of polyethyleneglycol and salt. From the dependence on DNA concentration of the CD signals, the anomalous CD of free DNA in polyethyleneglycol/salt solution was attributed to the intermolecular association of DNA molecules. The CD spectral changes in polyethyleneglycol/salt solution of the DNA - polylysine complex were indistinguishable from those of free DNA while the DNA-polyarginine complex suffered much smaller spectral changes as compared with free DNA, at low DNA concentrations where time-independent CD spectra were observed in polyethyleneglycol/salt solution for both the complexed and free DNA. The repression of the spectral change by the latter complex was more remarkable at higher ratios of polyarginine to DNA. The facts indicate that, whereas polylysine binding has little influence on the intermolecular structural transition of double-stranded DNA into a compact molecular configuration in polyethyleneglycol/salt solution, polyarginine binding has an effect of inhibiting the transition.

Animals↗