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     

Studies on well-coupled Photosystem I-enriched subchloroplast vesicles — energy-dependent switching between two different active states of the proton-translocation adenosine triphosphatase

Single-turnover flash-induced ATP synthesis coupled to natural cyclic electron flow in Photosystem I-enriched subchloroplast vesicles (from spinach) was continuously followed by the luciferin-luciferase luminescence. The ATP yield per flash was maximal (1 ATP per s per 1000 Chl) around a flash frequency of 0.5–2 Hz. It decreased both at lower and higher flash frequencies. The decrease at high flash frequency was due to limitation by the electron-transfer rate, while the decrease at low flash frequency was directly due to intrinsic properties of the ATPase itself. Carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP) decreased the yield at low frequency more than at high frequency. The same behaviour was observed if electron transfer was artificially mediated by pyocyanin. If the ADP concentration was increased from 40 to at least 80 μM, or if the vesicles were preincubated with 5 mM dithiothreitol (DTT), the decrease of the yield at flash frequencies below 0.5 Hz was no longer observed. Incubation with DTT increased the rates of ATP hydrolysis and synthesis at any flash frequency. The decrease of the yield could be elicited again by addition of 50 nM FCCP. It is concluded that at low levels of the protonmotive force (Δ gm_H⁺), the ATPase is converted into an active ATP-hydrolyzing state in which ATP synthesis activity is decreased due to a decreased affinity towards ADP and/or to a decreased release of newly synthesized ATP, that can be cancelled by increasing the ADP concentration or by addition of DTT in the absence of uncoupler.     

Transformation and growth related changes in levels of nuclear and cytoplasmic proteins antigenically related to mammalian beta-galactoside-binding lectin

Immunofluorescence and immunoblotting experiments, using a monoclonal antibody to the 13 kDa mammalian beta-galactoside-binding lectin have shown that human lymphocytes contain nuclear and cytoplasmic proteins of apparent molecular masses of 130, 80, 65 and 13 kDa that are antigenically related to the lectin and whose levels and patterns of expression change in association with transformation, or after stimulation with mitogens. These observations, together with the finding that the myeloid cell line K562 is also rich in the 130 kDa component, whereas the mature granulocytes of normal donors and of patients with chronic myeloid leukaemia are lacking in all of the immunoreactive forms, raise the possibility that this family of lectin-related proteins may be components of growth regulatory systems that are variously elicited in the transformed and stimulated cells.     

Evolution of the lipoprotein gene in the enterobacteriaceae. Cloning and DNA sequence of the lpp gene from Proteus mirabilis

We cloned the lipoprotein gene from Proteus mirabilis and determined its DNA sequence. Comparison with the lpp genes from Escherichia coli, Serratia marcescens, Erwinia amylovora and Morganella morganii revealed several unique features of the evolution of the lpp gene in the Enterobacteriaceae and enabled us to establish phylogenetic relationships between these bacteria.     

Lens cell-to-cel channel protein: II. Conformational change in the presence of calmodulin

Summary Lens fibers are coupled by communicating junctions, clusters of cell-to-cell channels composed of a 28-kD intrinsic membrane protein (MIP26). Evidence suggests that these and other cell-to-cell channels may close as a result of protein conformational change induced by activated calmodulin. To test the validity of this hypothesis, we have measured the intrinsic fluorescence emission and far-ultraviolet circular dichroism of the isolated components MIP26, calmodulin, and the MIP26-calmodulin complex, both in the absence and presence of Ca⁺⁺, an uncoupling agent. MIP26 shows no change in either, fluorescence emission (primarily tryptophan and a measure of aromatic constitutivity) or in its circular dichroism spectrum. Calmodulin exhibits a 32% increase in fluorescence emission intensity with constant emission wavelength, entirely tyrosine, and a 44% increase in -helicity, changes previously described. The MIP26-calmodulin complex, on the other hand, displays fluorescence emission and circular dichroism spectra which are slightly different from the sum of the two single components, but shows marked differences in both spectra upon Ca⁺⁺ addition. This indicates a change in conformation in one or both of the two components. Spectral changes include a 5-nm blue-shift, a 50% increase in tyrosine fluorescene emission, a 25% decrease in tryptophan fluorescence emission, and a 5% increase in the -helicity of the complex. These changes also occur about an isosbestic point and are fully reversible. These data provide additional evidence that activated calmodulin may modulate gating of cell-to-cell channels by affecting channel protein.     

Nitrobenzylthioinosine binding in brain: an interspecies study

The binding of the potent adenosine uptake inhibitor [3H]nitrobenzylthioinosine ( [3H]NBI) to cerebral cortical membrane preparations from human, dog, guinea pig, rat, and mouse was investigated. Reversible, specific, saturable, high affinity binding was found in all five species with similar kinetic parameters. (Kd = 0.16-0.44 nM; Bmax = 128-196 fmol/mg prot.). Dilazep, hexobendine, and dipyridamole were all high potency inhibitors of [3H]NBI binding in human, dog, guinea pig and mouse preparations but not in rat. These compounds showed a competitive inhibition of [3H]NBI binding indicating that they are acting at the same site. Discrepancies seen in the rat appear to be a unique, species related anomaly. The dihydropyridine calcium antagonists also inhibited binding with lower potency than the adenosine uptake blockers. This inhibition was most potent in dog and human and suggests a relationship between the calcium channel and the adenosine uptake site.     

Pancreatic islets of variable size--insulin secretion and glucose utilization

Glucose metabolism and insulin secretion were studied in isolated rat pancreatic islets of different sizes and the amount of tissue was quantitated by the measurement of DNA. It was found that larger islets (140-210 ng DNA/islet) utilized more glucose (based on the conversion of 3H-5-glucose to [3H]20) per ng of DNA than islets containing less DNA (60-120 ng/islet). However, the insulin secreted per ng of DNA in response to a given glucose concentration was the same in islets of all sizes. Also, the islet insulin and glucagon content when expressed in terms of DNA did not depend upon islet size. Thus, although glucose utilization rates expressed as a function of islet DNA content were greater in larger islets, no such relationship was found for glucose-induced insulin release or insulin and glucagon content.     

Phylogenetic Survey of Proteins Related to Synapsin I and Biochemical Analysis of Four Such Proteins from Fish Brain

A phylogenetic survey of proteins immunologically related to Synapsin I, a major synaptic vesicle-associated phosphoprotein in mammals was carried out. Proteins antigenically related to Synapsin I were found by use of radioimmunoassay and other radioimmunochemical techniques in the nervous systems of several vertebrate and invertebrate species, which included birds, reptiles, amphibians, fish, echinoderms, arthropods, and mollusks. Four proteins present in fish brain, antigenically related to Synapsin I, were further studied and found to resemble mammalian Synapsin I in several respects. Like Synapsin I, the fish proteins were present in high amounts in nervous tissue, were enriched in synaptosomal fractions of brain where they were substrates for endogenous protein kinases, were acid extractable, and were sensitive to digestion by collagenase. In addition, two-dimensional peptide-mapping analysis revealed some homology between major phosphopeptide fragments of Synapsin I and the fish proteins. The results indicate that proteins related to Synapsin I are wide-spread in the animal kingdom.     

Cholinergic- and Adrenergic-Stimulated Inositide Hydrolysis in Brain: Interaction, Regional Distribution, and Coupling Mechanisms

Carbachol and norepinephrine were used as agonists to compare and contrast cholinergic and adrenergic stimulation of inositide breakdown in rat brain slices. Carbachol acts through a muscarinic (possibly M1) receptor and norepinephrine acts through an alpha 1 adrenoceptor. Studies in cerebral cortical slices indicated that both agonists stimulated the production of inositol-1-phosphate and glycerophosphoinositol. Although the initial rates for the stimulation of inositol phosphate release were similar for the two ligands, the response to norepinephrine continued for 60 min and was larger compared with carbachol which plateaued at 30 min. The presence of carbachol did not affect the ED50 for norepinephrine. Concentrations of carbachol near the ED50 in combination with norepinephrine resulted in an additive response whereas maximal concentrations of carbachol and norepinephrine resulted in a less than additive response in the cortex. This negative interaction was also seen in the hippocampus and hypothalamus but not in the striatum, brainstem, spinal cord, olfactory bulb, or cerebellum. Norepinephrine had a larger response than carbachol in the hippocampus, striatum, and spinal cord, but the reverse was true in the olfactory bulb. Manganese (1 mM) stimulated the incorporation of [3H]inositol into phosphatidylinositol (PtdIns) four- to fivefold but not into polyphosphoinositides. The stimulation by manganese of PtdIns labelling increased the nonstimulated release of inositol phosphates but did not affect the stimulated release of inositol phosphates by carbachol or norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characteristics of the relative maximum in the decay of delayed light emission from Pothos leaf following far-red excitation

Following illumination with wavelengths longer than 700 nm, the intensity of light emission from Pothos aurea leaf falls for 1 min and then increases to a maximum after 2 min in the dark. The spectrum of this minute-range liminescence matches that of prompt fluorescence excited at the same wavelength, but differs from that of prompt or minute-range delayed emission excited by wavelengths shorter than 700 nm. This emission is less sensitive to heat damage than millisecond delayed emission, and may originate from photosystem I.