The International journal of biochemistry最新文献

1. To study the expression of a ferredoxin gene in extra-adrenocortical tissues, the amounts and structures of the ferredoxin gene transcripts in bovine liver and brain were studied and compared to those of that in adrenocortex. 2. The sizes and amounts of the ferredoxin mRNAs were analyzed by means of Northern blotting, RNA slot blotting and RT-PCR. 3. The nucleotide sequences were determined for 39 ferredoxin cDNA clones from bovine liver. 4. The results indicated that the sizes of the ferredoxin mRNAs in liver and brain were the same as that in adrenocortex, however, their amounts were approx 1/30th and less than the latter, respectively. 5. Although the multiple forms of ferredoxin cDNA, differing in the poly(A) addition sites, were also found in liver, a minor form of ferredoxin cDNA, produced through alternative promoter usage and splicing, could not be detected in liver. 6. The nucleotide sequences of all hepato-ferredoxin cDNA clones obtained were identical to that of a major type of adreno-ferredoxin. 7. These results showed that the expression level of the ferredoxin gene in different tissues was controlled by the amount of mRNA.

Ferrous iron uptake was investigated in Bifidobacterium thermophilum (B. thermophilum) in the presence of Mg2+ and Ca2+ with the following findings: 1. Mg2+ inhibited Fe2+ accumulation in the cells in a dose-dependent manner at 37 degrees, but not at 0 degrees. Removal of Mg2+ from the medium resulted in a resumption of rapid iron uptake. 2. Mg2+ had no effect on the binding of Fe2+ by B. thermophilum protoplasts, its cellular particulate fraction, or distribution between the particulate and soluble fractions. 3. Ca2+ exerted a stimulatory effect on iron uptake by B. thermophilum, but was not able to reverse the inhibitory effects of Mg2+. 4. It was concluded that Mg2+ has no effect on the binding of iron on the surface or interior of B. thermophilum and that it affected the Fe2+ transport mechanism (permease) in a reversible manner. It is possible that iron and magnesium share the same permease in this microorganism.

1. Specific antibodies against a whole preparation of glycophorins from rat erythrocyte membrane and against its most prominent component (32 kDa) were prepared. 2. Both antisera and the respective affinity-purified antibodies recognize the 74, 32 and 25 kDa components of rat glycophorins; therefore, a close antigenic relationship between them can be inferred. 3. On the other hand, a cross-reaction with human glycophorin A (both MM- and NN-type) is observed for both antisera. 4. This suggests the existence of epitopes common to human and rat glycophorins.

1. Fe(III)-citrate forms a red coloured complex with bovine serum albumin (lambda max = 500 nm). 2. Fe(III)-albumin complexes also appear, when Fe(III)-citrate is mixed with albumin, suggesting that albumin competes with citrate for ferric ions.

1. This paper studies the effect of thyroid status on 5'-D activity in pineal gland, Harderian gland, brown adipose tissue (BAT), pituitary gland, brain frontal cortex (BFC), and cerebellum. 2. Hypothyroidism clearly increased diurnal 5'-D activity in Harderian gland, BAT, pituitary gland, BFC, and cerebellum. In pineal gland, diurnal values of 5'-D activity were not affected by hypothyroidism. 3. Hypothyroidism in adult rats clearly enhanced nocturnal increase of 5'-D activity in pineal and Harderian gland. Congenital hypothyroidism also enhanced the nocturnal increase of 5'-D activity in pineal gland. 4. Hyperthyroidism inhibited 5'-D activity in pituitary gland, BFC, and cerebellum. A small inhibition, although significant, was found in BAT. 5. In pineal and Harderian gland, hyperthyroidism did not inhibit either the basal diurnal values of the enzyme or the nocturnal increase of its activity. 6. Results suggest that, in tissues where 5'D-activity is regulated by adrenergic mechanisms, mostly pineal gland and Harderian gland, the enzyme activity is independent of serum T4 concentrations during hyperthyroidism.

1. DNA polymerase alpha (pol alpha) isolated from Simian virus 40 (SV40)-transformed cells showed more than 3-fold higher specific activity than pol alpha from normal cells. The enzymes from untransformed and transformed cells also differed in molecular size, thermolability, sensitivity to inhibitors and specificity of template-primer utilization. 2. Western analysis using anti-Tag to probe both a crude cell homogenate and partially purified pol alpha from SV40 transformed cells showed multiple immunoreactive bands with different molecular sizes. 3. While alpha polymerases from both normal and transformed cells exhibited tightly associated primase activity, they showed different DNA binding affinities. 4. These data suggest that T antigen binding to pol alpha alters the initiation of DNA replication and/or the function of pol alpha in SV40-transformed cells, and that pol alpha from SV40-transformed human fibroblasts have different catalytic subunit characteristics than pol alpha from untransformed cells.

1. Two calcyclin fragments were obtained by CNBr-cleavage. 2. One fragment represented N-terminal end of a molecule (residues 1-56), and another one a C-terminal end (residues 57-89). 3. Properties of intact calcyclin such as binding of calcium, binding to hydrophobic resins and interaction with calcyclin specific antibodies were not retained by these fragments. 4. However, both fragments were able to form dimers and higher forms of aggregates as seen for uncleaved calcyclin. 5. This indicates that both halves of the molecule contain the regions responsible for non-covalent interaction which might participate in dimer formation.

1. The excitation and emission maxima of nile red in the presence of LDL were found to be 526 and 587 nm, respectively. Oxidation of LDL for 16 hr in the presence of CuSO4 resulted in significant spectral shifts to longer wavelengths in both the excitation and emission spectra. 2. The difference in the fluorescence intensity between native and oxidized LDL was most pronounced at wavelengths between 550 and 580 nm. At these emission wavelengths, the relative fluorescence intensity of nile red treated oxidized LDL was found to be decreased by approx 30% when compared to that observed in the presence of native LDL. 3. Differences in the nile red fluorescence spectra were not observed when LDL and acetylated LDL were compared.

1. Matrix-immobilized calcyclin as affinity ligand in chromatography led to purification of three protein bands at 68, 36 and 35 kDa from bovine heart that required Ca2+ for binding. 2. Polyacrylamide-immobilized phosphatidylserine separated this fraction into a phospholipid-binding part (68 kDa, 35 kDa), also attaching to phospholipid vesicles even in the presence of calcyclin, and a flow-through part, constituting approx 30% of the total fraction (36 kDa). 3. Enzyme assays and electrophoretic mobility showed an at least close relationship of the 36 kDa band to glyceraldehyde-3-phosphate dehydrogenase. Interaction between enzyme and calcyclin in a solid-phase assay was inhibited by sialoglycoproteins and depended strongly on the integrity of carboxyl and hydrophobic groups of the enzyme. The interaction between the two proteins had a KD value of 110 nM. 4. Application of annexin-specific antibodies revealed an immunological relationship of the 35 and 68 kDa calcyclin-binding proteins to members of the annexin family, namely to annexin II (35 kDa) and annexin VI (68 kDa). The N-terminal amino acid sequence of a cleavage peptide of the 68 kDa protein was identical to a sequence stretch in human annexin VI, corroborating this evidence.

1. alpha-Macroglobulins (alpha Ms) were isolated from the serum of injured rats through a two-stage method: gel filtration and ultracentrifugation. 2. The clearance rates of rat plasma kallikrein (RPK) and alpha Ms-RPK complexes were compared in an isolated rat liver perfusion system: the alpha Ms-RPK complexes are cleared at a much slower rate (half-life ranging from 24 to > 120 min) than does RPK itself (half-life ranging from 13 to 18 min).