Acta biochimica et biophysica; Academiae Scientiarum Hungaricae最新文献

Long-lived emission spectra and delayed fluorescence decay curves of flavomononucleotide (FMN) in poly(vinyl alcohol) film (PVA) at room temperature were measured. Pulsed N2-laser excitation was used. It was found that the FMN complexes stabilized by PVA matrix show delayed fluorescence (band at about 540 nm) and phosphorescence (band at about 640 nm). The decay curves of the delayed fluorescence are two-exponential with decay times tau 1 = 62 +/- 1 ms and tau 2 = 15 +/- 1 ms.

The proteolysis of rabbit skeletal muscle phosphorylase b was studied with Sepharose 4B bound subtilisin BPN' in the absence and presence of various ligands. The proteolysis was carried out at pH 7.0 and pH 8.5 and was followed by measuring phosphorylase b activity and by SDS gel electrophoresis. The effect of ligands proved to be qualitatively the same at both pH values. It was found that AMP and alpha-D-glucose-1-phosphate accelerated the inactivation of phosphorylase b by subtilisin, two main proteolytic products (Mr 70 000 and 30 000) were formed in the presence of these ligands. IMP and glycogen protected phosphorylase b against proteolytic attack. Subtilisin treatment in the presence of D-glucose, caffeine and D-glucose-6-phosphate produced a reproducible increase (about 20%) of phosphorylase b activity. This "activation" resulted in an increased Vmax of phosphorylase b though did not alter the subunit size, the aggregation state and the ligand binding capacity of the enzyme.

Nail samples of 157 adult Hungarian twin pairs were examined for different trace elements by neutron activation analysis. Comparing the within-pair-concordance for zinc contents of the twins of different zygosity, a much higher concordance in monozygotes than in dizygotes was observed. The authors suggest the idea that the zinc content in the human organism, at least in some organs, may be genetically controlled.

Phosphorescence spectra at 103 K and delayed fluorescence and phosphorescence spectra at 296 K of flavomononucleotide (FMN) stabilized by poly(vinyl alcohol) PVA matrix have been measured. At 103 K the FMN monomer and excimer exhibit phosphorescence bands at about 620 and 640 nm, respectively. At 295 K the delayed fluorescence and phosphorescence of the FMN excimer exist together, revealing that FMN in the excited triplet state is an energetically well-isolated molecular complex which may play an important role in photobiological reactions.

Such details of the primary structure were sought that are common in all dehydrogenases of known amino acid sequence. Twenty-six sequences of eight kinds of dehydrogenase (D-glyceraldehyde-3-phosphate dehydrogenase, alcohol dehydrogenase, lactate dehydrogenase, glutamate dehydrogenase, glycerol-3-phosphate dehydrogenase, ribitol dehydrogenase, L-hydroxyacyl-CoA dehydrogenase and homoserine dehydrogenase) have been compared by the aid of the artificial intelligence language Prolog, the amino acids being classified into groups according to their chemical properties, and alpha-helix or beta-sheet-forming abilities. We found tetrapeptides that occurred in all dehydrogenases examined. By using these tetrapeptides as markers a population of 84 partial sequences has been described. The partial sequences constituting this population are peptides comprising 35 residues. It has been shown statistically that these peptides form a homogeneous sample as regards the frequency of occurrence of amino acid groups. This statistically homogeneous partial sequences can be regarded as homologous and it is assumed that their presence is characteristic of dehydrogenases.

Fractionation on sucrose gradients of nuclear described extracts prepared from cultured Drosophila melanogaster cells by sonication of the nuclei in the presence of rat liver cytosol RNAase inhibitor revealed a complex polysome-like pattern of nuclear ribonucleoprotein complexes. The bulk of these heterogeneous ribonucleoprotein (hnRNP) complexes sedimented in the 30S to 80S zone of the sucrose gradient. According to biochemical and morphological data, the monomer particle proved to be the 45S hnRNP and its average diameter was found by electron microscopy to be 24-26 nm. The buoyant density of both the mono and polyparticles was about 1.4 g/cm3, with a slight degree of heterogeneity. The proteins from different zones of the sucrose gradient were composed primarily of similar polypeptides of 47 000, 56 000, 64 000, 96 000 and 130 000 daltons. Complete dissociation of nuclear hnRNP complexes was observed by resedimentation of the particles in the presence of 0.7 M NaCl or 4 M urea. RNAase A digestion (0.1 microgram/ml at 0 degree C for 10 min) resulted in the solubilization of part of the hnRNP and aggregation of some particles. The bulk of the RNA isolated from the different sized hnRNP complexes sedimented in the 7 to 11S region in the sucrose gradient. The large hnRNP complexes contained hnRNA strands larger than 15S, up to 28S. The base composition of the RNA from the 45S monoparticles proved to be AU type: A + U/G + C = 1.7. The RNAs from the 60-75S and 90- 100S polyparticles were also AU type, with an A + U/G + C ratio of 1.46 and 1.21, respectively. The hnRNP complexes exhibited marked heterogeneity in the electron microscope. Our biochemical and morphological observation point to a nonrandom organization of hnRNP particles in Drosophila melanogaster nuclei.

The NAD-induced local conformational changes in the fluorescent dye-binding region of muscle glyceraldehyde-3-phosphate dehydrogenase were studied (Ovádi et al., 1982). We have isolated a dominant peptide containing the fluorescent dye from the tryptic digest of labelled dehydrogenase, and identified this labelled amino acid residue. The data indicate that fluorescein isothiocyanate can react rather specifically with tyrosyl residue 91, which is not associated with the catalytic function of the enzyme. Tyrosyl-91 modified by the fluorescent dye does not interact directly with any part of the NAD bound at the active site of glyceraldehyde-3-phosphate dehydrogenase.