Interconversion of F430 derivatives of methanogenic bacteria

F₄₃₀ is the prosthetic group of the methylcoenzyme M reductase of methanogenic bacteria. The compound isolated from Methanosarcina barkeri appears to be identical to the one obtained from the only distinctly related Methanobacterium thermoautotrophicum. F₄₃₀ is thermolabile and in the presence of acetonitrile or C10 _in4 ^sup- two epimerization products are obtained upon heating; in the absence of these compounds F₄₃₀ is oxidized to 12, 13-didehydro-F₄₃₀. The latter is stereoselectively reduced under H₂ atmosphere to F₄₃₀ by cell-free extracts of M. barkeri or M. thermoautotrophicum. H₂ may be replaced by the reduced methanogenic electron carrier coenzyme F₄₂₀.Abbreviations CH₃S-CoM methylcoenzyme M, 2-methylthioethanesulfonic acid - HS-CoM coenzyme M, 2-mercaptoethanesulfonic acid - F₄₃₀ Ni(II) tetrahydro-(12, 13)-corphin with a uroporphinoid (III) ligand skeleton - 13-epi-F₄₃₀ and 12,13-di-epi-F₄₃₀ the 12, 13- and 12, 13-derivatives of F₄₃₀ - 12, 13-didehydro-F₄₃₀ F₄₃₀ oxidized at C-12 and C-13 - coenzyme F₄₂₀ 7,8-didemethyl-8-hydroxy-5-deazaflavin derivative - coenzyme F₄₂₀H₂ reduced coenzyme F₄₂₀ - MV⁺ methylviologen semiquinone - HPLC high-performance liquid chromatography     

The tertiary structure of Aspergillus saitoi minor ribonuclease (Ms) predicted from the structure of RNase T1

Ribonuclease Ms from Aspergillus saitoi is a small acidic protein (11 714 Da) containing 106 amino acids of known sequence. Unlike other enzymes belonging to the RNase T₁ family this ribonuclease is base-unspecific. Using interactive computer graphics and energy minimisation we predicted the structure of RNase Ms on the basis of sequence homology to RNase T₁ of known structure. In this report the predicted structure of this protein is presented and characterised.     

The primary structures of ribosomal proteins L16, L23 and L33 from the archaebacterium Halobacterium marismortui

The complete amino acid sequences of ribosomal proteins L16, L23 and L33 from the archaebacterium Halobacterium marismortui were determined. The sequences were established by manual sequencing of peptides produced with several proteases as well as by cleavage with dilute HCl. Proteins L16, L23 and L33 consist of 119, 154 and 69 amino acid residues, and their molecular masses are 13538, 16812 and 7620 Da, respectively. The comparison of their sequences with those of ribosomal proteins from other organisms revealed that L23 and L33 are related to eubacterial ribosomal proteins from Escherichia coli and Bacillus stearothermophilus, while protein L16 was found to be homologous to a eukaryotic ribosomal protein from yeast. These results provide information about the special phylogenetic position of archaebacteria.     

Secretion of a new growth factor, smooth muscle cell derived growth factor, distinct from platelet derived growth factor by cultured rabbit aortic smooth muscle cells

In attempts to determine the mechanism of proliferation of arterial smooth muscle cells (SMC) in intimal atheromatous lesions, autocrine secretion of growth factors by SMC has recently received much attention. Here we report a new growth factor named smooth muscle cell derived growth factor (SDGF). Cultured rabbit medial SMC secreted SDGF for 1 week during their incubation in serum-free media only after at least 4 passages. SDGF differed from platelet derived growth factor (PDGF) physicochemically, immunologically, and biologically. The properties of SDGF also seemed different from those of other known growth factors that stimulate the proliferation of mesenchymal cells.     

Chicken liver basic fatty acid-binding protein (pI = 9.0). Purification, crystallization and preliminary X-ray data

Chicken liver basic fatty acid-binding protein (pI = 9.0) has been purified with a high yield by a modification of a method originally applied to rat liver. The final product is highly homogeneous and can be used to grow crystals that belong to two different space groups. The crystals are either tetragonal, space group P4₂2₁2 with a = b = 60.2 Å and c = 138.1 Å or orthorhombic, space group P2₁2₁2₁ with a = 60.7 Å, b = 40.1 Å and c = 66.7 Å. The second form appears to be more suitable for X-ray diffraction studies, it diffracts to at least 2.8 Å resolution and it is believed to contain one protein molecule in the crystallographic asymmetric unit.     

Generation of phosphatidylinositol 4,5-bisphosphate proceeds through an intracellular route in rat hepatocytes

The subcellular distribution in rat hepatocytes of enzymes participating in the entire generation cycle of phosphatidylinositol 4,5-bisphosphate, and phosphorylated intermediates of this pathway, has been examined by Nycodenz gradient centrifugation. Our results indicate that the synthesis of phosphatidylinositol takes place in the endoplasmic reticulum, and that its phosphorylation to phosphatidylinositol 4-phosphate occurs intracellularly in low-density membranes before translocation to the plasma membrane, where it is further phosphorylated to phosphatidylinositol 4,5-bisphosphate. The intracellular formation of PIP implies a vesicular transport to the plasma membrane.     

Human heart cytochrome c oxidase subunit VIII. Purification and determination of the complete amino acid sequence

Subunit VIII was purified from a preparation of the human heart cytochrome c oxidase and its complete amino acid sequence was determined. The sequence proved to be much more related to that of the bovine liver oxidase subunit VIII than to that found in bovine heart. Our finding of a ‘liver-type’ subunit VIII in the human heart enzyme suggests that either there are no isoforms of human subunit VIII or the human oxidase does not show the type of tissue specificity that has been reported for the oxidase in other mammals.     

The interaction of MgADP with H-ATPase in rat liver mitochondria

The activating anions are found to induce an unexpectedly high (up to 8-fold for sulphite) increase of ATPase activity in intact rat liver mitochondria. This effect is not determined by the observed changes in K_m and K_i (ADP) values. The stimulation seems to be caused by dissociation of the inactive complex of ATPase with Mg·ADP. The quantity of this complex formed in the course of ATP hydrolysis is approx. 90% of the total ATPase content in intact mitochondria. The data on toluene-permeabilized mitochondria suggest that the high content of the complex is a result of the stabilizing effect of some matrix macromolecules.     

Identification of a deletion in the LDL receptor gene A Finnish type of mutation

A cDNA probe for the low density lipoprotein (LDL) receptor gene was used to screen DNA samples from 52 unrelated Finnish patients with the heterozygous form of familial hypercholesterolemia (FH) and 51 healthy controls. Southern blot analysis using the restriction enzyme PvuII revealed an abnormal 11 kb (kilo base-pair) restriction fragment in 16 (31%) of the patients but none of the controls. A more detailed restriction enzyme analysis of the DNA from patients revealed a mutation which apparently is due to an 8 kb deletion extending from intron 15 to exon 18 of the LDL receptor gene. Co-segregation of FH with the mutated gene was demonstrated in three families. These data are consistent with a ‘founder gene effect’ and support the assumption that recombinant DNA methods may have great impact on the diagnostics of FH in genetically homogeneous populations.     

Homosexual male pairing in Schistosoma mansoni

and 1988. Homosexual male pairing in Schistosoma mansoni.International Journal for Parasitology 18: 1115–1117. To see whether male worms within the gynecophoral canal of another male worm would become feminized (i.e. express vestigial female-associated genes), we established homosexual pairs by twice exposing mice to male cercariae with a 4 or 6-week interval, and perfusing 3–5 weeks later. From 13 to 34% of these worms were found in pairs, compared with 0 to 7% in singly exposed controls. ‘Inner’ males in homosexual pairs showed no histological evidence of female reproductive structures, but were stunted, had poorly developed testes, and the high nuclear density characteristic of mature females. More vitelline follicles occurred in unpaired unisexual males than in homosexually paired males, fewest in bisexually paired males. Uptake of tyrosine, an indicator of vitelline development, occurred in the same relative order. The gynecophoral microenvironment often led to stunting, probably through starvation induced by the relative inaccessibility of host blood to homosexually clasped males.