Glucose-6-phosphate dehydrogenase porbandar: A new slow variant with slightly reduced activity in a South African family of Indian descent

A new variant of the red cell enzyme glucose-6-phosphate dehydrogenase has been detected in a South African male of Indian descent and in several of his relatives. The enzyme variant is characterized by slow electrophoretic mobility, low Michaelis constants for the substrates glucose-6-phosphate and NADP, and increased utilization of the substrate analogues 2-deoxyglucose-6-phosphate and deamino-NADP relative to the normal (B⁺) enzyme. There is no evidence that the enzyme variant, for which the name G6PD Porbandar is suggested, is associated with any hematological abnormality.The Atomic Energy Board and the South African Medical Research Council provided support for part of this work.     

Composition of the cell wall of Chlorella fusca

Isolated cell walls of mature Chlorella fusca consisted of about 80% carbohydrate, 7% protein, and 13% unidentified material. Mannose and glucose were present in a ratio of about 2.7:1 and accounted for most of the carbohydrate. Minor components were glucuronic acid, rhamnose, and traces of other sugars; galactose was absent. After treatment with 2 M trifluoroacetic acid or with 80% acetic acid/HNO₃ (10/1, v/v), a residue with a mannose/glucose ratio of 0.3:1 was obtained, probably representing a structural polysaccharide. An X-ray diffraction diagram of the walls showed one diffuse reflection at 0.44 nm and no reflections characteristic of cellulose. Walls from young cells contained about 51% carbohydrate, 12% protein, and 37% unidentified material. Mannose and glucose were also the main sugars; their absolute amounts per wall increased 6–7 fold during cell growth. Walls isolated with omission of a dodecylsulphate/mercaptoethanol/urea extraction step had a higher protein content and, with young walls, a significantly higher glucose and fucose content. These data and other published cell wall analyses show a wide variability in cell wall composition of the members of the genus Chlorella.Abbreviations GLC gas liquid chromatography - TFA trifluoroacetic acid     

Time-dependent changes of calcium influx and efflux rates in rabbit skeletal muscle sarcoplasmic reticulum

Unfractionated and low buoyant density sarcoplasmic reticulum vesicles released calcium spontaneously after ATP- or acetyl phosphate-supported calcium uptake when internal Ca²⁺ was stabilized by the use of 50 mM phosphate as calcium-precipitating anion. This spontaneous calcium release could not be attributed to falling Ca²⁺ concentration outside the vesicles (Ca₀²⁺), substrate depletion, ADP accumulation, nonspecific membrane deterioration or the attainment of a high vesicular calcium content. Instead, spontaneous calcium release was directly proportional to Ca₀²⁺ at the time that calcium content was maximal. A causal relationship between high Ca₀²⁺ and spontaneous calcium release was suggested by the finding that elevation of Ca₀²⁺ from less than 1 μM to 3–5 μM increased the rate and extent of calcium release.The spontaneous calcium release was due both to acceleration of calcium efflux and slowing of calcium influx that was not accompanied by a significant change in the rate of ATP hydrolysis. Neither reversal of the transmembrane KCl gradient nor incubation with cation and proton ionophores abolished the spontaneous calcium release. The persistence of calcium release under conditions where the membrane was permeable to both anions and cations makes it unlikely that this phenomenon is due to a changing transmembrane potential.     

Detection and discrimination of individual viruses by flow cytometry.

A new flow cytometer with a very small observation volume has been developed to detect individual viruses with good resolution, and has been used to discriminate between two types of viral particles based on differences in their light scattering. Measurements of light scattering and fluorescence made with such an instrument can provide a basis for quantitative analysis and sorting of viruses and other particles in the micron and submicron size range.     

A search for the indianapolis-variant of human alcohol dehydrogenase in liver autopsy samples from North Germany and Japan

Summary Human liver alcohol dehydrogenase (ADH) variants were screened in random autopsy specimens from 53 North German and 34 Japanese individuals. Based on pH-activity profile and electrophoretic pattern, only ADH₂ and ADH₃ variants were detected. In relatively fresh specimens, an anodic band or -ADH band was also observed. The recently reported new molecular forms collectively called ADH_Indianapolis (Bosron et al. 1980) could not be demonstrated and therefore may be confined hitherto only to the American black population.This paper is dedicated to Professor Dr. Dr. H. Baitsch on his 60th birthday     

Nuclear magnetic resonance study of the impact of ribose 2′-O-methylation on the aqueous solution conformation of cytidylyl-(3′ → 5′)-cytidine

In order to obtain information about the conformational characteristics at the nearestneighbor level in the 2′-O-methylated region of t-RNA, as well as in the bizarre 5′-terminus of eucaryotic mRNA, a detailed nuclear magnetic resonance study of 2′-O-methyl-cytidylyl-(3′ → 5′)-cytidine (CmpC) was conducted. Proton spectra were recorded at 270 MHz in the Fourier mode in D₂O solutions, 0.01M, pD 7.3 in the temperature range 5–80°C. Complete accurate sets of nmr parameters were derived for each of the nucleotidyl units by a combination of homo-nuclear decouplings and simulation iteration methods. The data were translated into conformational parameters using procedures developed in earlier studies from these laboratories. It is shown that the ribofuranose ring exists at a ²E ? ³E equilibrium with clear preference [(75–80)%] for the ³E mode. The C(4′)-C(5′) and C(5′)-O(5′) bonds form a stable conformational network with outspoken preference for conformers in which Ψ₁, Ψ₂ ? 60° and ?₂ ? 180°. The orientation of the 3′-phosphate and 2′-O-methyl groups is such that ?₁′ ? 210° and ?″ ? 60°. The phosphodiester bonds are flexible and shift trends for base, H(1′), and H(5″) suggest the existence of a conformational blend of right-handed stack (g^?g^?), left-handed stack (g⁺g⁺), and unstacked arrays (tg^? and tg⁺). Elevation of temperature perturbs the ²E ? ³E equilibrium accompanied with modest depopulation of ψ₁, ψ₂ ? 60° and ?₂ ? 180° conformers. The major effect of elevation of temperature is in the increase of unstacked arrays at the expense of g^?g^? and g⁺g⁺ conformers. The shift trend of Cmp-H(3′) with temperature shows that torsional variation about O(3′)-P is facilitated by increase in temperature and the preferred rotamer about O(3′)-P in the unstacked form is t (ω₁′ = 180°). A detailed comparison of the aqueous solution conformations of CpC and CmpC reveals that 2′-O-methylation causes: (i) a reduction in the magnitude of _χ1; (ii) an increase in the population of ³E pucker at the 3′-nucleotidyl unit; and (iii) modest perturbations in the O(3′)-P and P-O(5′) bond conformations. Comparison of the aqueous solution conformations of AmpA and CmpC makes clear that the conformational properties of pyrimidine-pyrimidine and purine-purine dimers which carry a 2′-O-methylated 3′-nucleotidyl unit are significantly different.     

Endogene Synthese kurzlebiger Messenger-RNS in der Oocyte vonDysdercus intermedius Dist. nach Abschluß der Vitellogenese

Zusammenfassung In den Oocyten des telotroph-meroistischen Ovars vonDysdercus intermedius Dist. findet während der Endphase der Oogenese, 4–14 h vor der Eiablage, eine Synthese von nichtribosomaler RNS statt. Eine in vivo-Markierung dieser RNS läßt sich erreichen, wenn radioaktive RNS-Vorstufen einem Nucleotidpool zugeführt werden, der im Ooplasma vor der Chorionbildung angelegt wird.Diese vor der Eiablage gebildete RNS zeichnet sich durch einen hohen Turnover aus. Sie erscheint zunächst in Form einer hochmolekularen Vorstufe und wird im Verlauf weniger Stunden in kleinere, nichtribosomale Moleküle mit S-Werten zwischen 30 und 5 umgewandelt. Im frisch abgelegten Ei fehlen RNS-Spezies, die dieser endogenen Oocytensynthese entstammen; es sind nur noch ihre Degradationsprodukte, die sich innerhalb der Nucleotidfraktion ansammeln, nachweisbar. Die endogen synthetisierte RNS wird demnach im Gegensatz zu der in den Nährzellen synthetisierten und im Ei in stabiler Form gespeicherten RNS nicht für einen Bedarf während der Embryogenese konserviert.Die endogen synthetisierte RNS zeichnet sich durch einen hohen Poly (A)-Gehalt aus; 57% hybridisieren mit an Glasfaserfiltern immobilisiertem Poly(U). Wenige Stunden vor der Eiablage findet man kurzlebige oocytäre RNS-Moleküle an Polysomen assoziiert. Die Inkubation dieser Polysomen in einem in vitro-Proteinsynthese-System liefert Polypeptide, deren Auftrennung am SDS-Polyacrylamid-Gel ein charakteristisches Bandenspektrum ergibt. Die Molekulargewichte der 4 Hauptbanden liegen bei 65000, 48000, 44000, und 40000. Keines dieser Proteine ist mit einem Chorionprotein identisch.Die Kurzlebigkeit, der relativ hohe Poly (A)-Gehalt sowie die Fähigkeit, die Proteinsynthese sowohl in vivo als auch in vitro zu aktivieren, spricht dafür, daß die spät-oocytär gebildete heterogene Population von RNS-Molekülen mRNS-Komponenten enthält.Bei Frl. Heidrun Greipel bedanken wir uns für die ausgezeichnète Assistenz.     

Photoelectric currents across planar bilayer membranes containing bacterial reaction centers. Response under conditions of single electron turnover.

Light-induced electric current and potential responses have been measured across planar phospholipid membranes containing reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides. Under conditions in which the reaction centers are restricted to a single electron turnover, the responses can be correlated with the light-induced electron transfer reactions associated with the reaction center. The results indicate that electron transfer from the bacteriochlorophyll dimer to the primary ubiquinone molecule, and from ferrocytochrome c to the oxidized dimer occur in series across the planar membrane. Electron transfer from the primary to secondary ubiquinone molecule is not electrogenic.