Pathways of proton transfer in the light-driven pump bacteriorhodopsin

The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood. Light causes the all-trans to 13-cis isomerization of the retinal chromophore. This sets off a sequential and directed series of transient decreases in the pKa's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96. The timing of these pKa changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.     

Metal complex formation by nicotianamine,a possible phytosiderophore

Summary The acid dissociation constants of nicotianamine (1) (pK₁=6.97, pK₂=9.13, pK₃=9.75; 0.1 M KClO₄, 25°C) and the stability constants for its 11 complexes with bivalent metal ions (log K_Cu=18.6, log K_Ni=16.1, log K_Co=14.8, log K_Zn=14.7, log K_Fe=12.1, log K_Mn=8.8, log K_Mg4.5; 0.1 M KClO₄, 25°C) were determined using potentiometric titrations in aqueous solution. Fe(III)-nicotianamine complexes were not detected under the same experimental conditions.Part 13 in the series On the normalizing factor for the tomato mutantchloronerva, for part 12 see Ripperger et al.⁴.     

Role of lysine side chains in metallothionein

Summary pK_a-Values of lysine residues of mammalian metallothionein were determined by chemical titration measurements of -CH₂ lysine resonances in the¹H-NMR spectra. They are about 0.5 pH-unit higher than the average pK_a-value of a metal-free derivative, suggesting interaction of the positively charged residues with the two three-fold negatively charged metal-thiolate clusters of the metal-containing form. Deprotonation of the lysines leads to circular dichroism changes attributable to an electrostatically induced structural transition of the protein.To whom correspondence concerning this paper should be addressed.     

The proton Compton wavelength as the ‘quantum’ of length

Résumé La plupart des longueurs expérimentales concernant les forces fondamentales dans le nucleus sont des multiples intégraux de la longueur d'onde Compton, ₀, du proton, où ₀=h/m ₀ c=1.32×10^–13 cm (qui peut ainsi s'appeler un « compton »). Ces longueurs comprennent la portée effective des interactions des nucléons, et les amplitudes de dispersion.On a également trouvé par différentes méthodes que le radius d'unité,R ₀, du nucleus se situe entre 1,0 et 1,5 × 10^–13 cm. Il semble donc que le vrai radius du proton peut bien être sa longueur d'onde Compton.     

Binding of aluminium ions byStaphylococcus aureus 893

Résumé Deux types de liaisons ont lieu quand des ions d'aluminium réagissent avec les parois cellulaires isolées deStraphylococcus aureus espèce 893. La première interaction a comme résultat la formation d'un complexe stable qui affecte des groupes occupant le mur de la cellule avec un pK _a 5. On suppose l'existence d'un composant de surface constitué par de la protéine combinée à de l'acide teichoique. La deuxième liaison consiste en ions interchangeables dans la couche mobile de cations recouvrant la paroi.     

Note on the strength of picric acid

Zusammenfassung Am Beispiel der Pikrinsäure wird gezeigt, wie man mit Hilfe optischer Messungen auch zu der thermodynamischen Aziditätskonstante von recht starken Säuren (pK 0) kommen kann.

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Special fellow of the U.S. Public Health Service, representing the National Institutes of Health.     

Role of <Emphasis Type="Italic">N</Emphasis>-linked polymannose oligosaccharides in targeting glycoproteins for endoplasmic reticulum-associated degradation

Misfolded or incompletely assembled multisubunit glycoproteins undergo endoplasmic reticulum-associated degradation (ERAD) regulated in large measure by their N-linked polymannose oligosaccharides. In this quality control system lectin interaction with Glc₃Man₉GlcNAc₂ glycans after trimming with endoplasmic reticulum (ER) -glucosidases and -mannosidases sorts out persistently unfolded glycoproteins for N-deglycosylation and proteolytic degradation. Monoglucosylated (Glc₁Man₉GlcNAc₂) glycoproteins take part in the calnexin/calreticulin glucosylation-deglucosylation cycle, while the Man₈GlcNAc₂ isomer B product of ER mannosidase I interacts with EDEM. Proteasomal degradation requires retrotranslocation into the cytosol through a Sec61 channel and deglycosylation by peptide: N-glycosidase (PNGase); in alternate models both PNGase and proteasomes may be either free in the cytosol or ER membrane-imbedded/attached. Numerous proteins appear to undergo nonproteasomal degradation in which deglycosylation and proteolysis take place in the ER lumen. The released free oligosaccharides (OS) are transported to the cytosol as OS-GlcNAc₂ along with similar components produced by the hydrolytic action of the oligosaccharyltransferase, where they together with OS from the proteasomal pathway are trimmed to Man₅GlcNAc₁ by the action of cytosolic endo--N-acetylglucosaminidase and -mannosidase before entering the lysosomes. Some misfolded glycoproteins can recycle between the ER, intermediate and Golgi compartments, where they are further processed before ERAD. Moreover, properly folded glycoproteins with mannose-trimmed glycans can be deglucosylated in the Golgi by endomannosidase, thereby releasing calreticulin and permitting formation of complex OS. A number of regulatory controls have been described, including the glucosidase-glucosyltransferase shuttle, which controls the level of Glc₃Man₉GlcNAc₂-P-P-Dol, and the unfolded protein response, which enhances synthesis of components of the quality control system.Received 26 January 2004; accepted 25 February 2004     

Studies on the reconstitution ofP. clarkii blue carotenoprotein from its isolated subunits

Summary A blue carotenoid-protein complex (_max 635 nm) was extracted and purified from the carapace of the crayfishProcambarus clarkii. The complex was further liberated from astaxanthin, its prostetic group, causing dissociation into apoprotein subunits. Reconstitution of the complex from the various sub-units (isolated by chromatofocusing) plus astaxanthin was attempted. Apoprotein-size pigments of rose-purple color (_max 545 nm) were obtained. It was found that both monomers are required in order to a blue complex fairly similar in structure ot the native one. However, the native conformation was not completely recovered, as indicated by some differences in the UV spectrum.     

Fatty acid metabolism in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Peroxisomes are essential subcellular organelles involved in a variety of metabolic processes. Their importance is underlined by the identification of a large group of inherited diseases in humans in which one or more of the peroxisomal functions are impaired. The yeast Saccharomyces cerevisiae has been used as a model organism to study the functions of peroxisomes. Efficient oxidation of fatty acids does not only require the participation of peroxisomal enzymes but also the active involvement of other gene products. One group of important gene products in this respect includes peroxisomal membrane proteins involved in metabolite transport. This overview discusses the various aspects of fatty acid -oxidation in S. cerevisiae. Addressed are the various enzymes and their particular functions as well as the various transport mechanisms to take up fatty acids into peroxisomes or to export the -oxidation products out of the peroxisome to mitochondria for full oxidation to CO₂ and H₂O.Received 19 February 2003; received after revision 27 March 2003; accepted 27 March 2003     

Cytogénétique desLeggada: (1) La formule chromosomique deMus (Leggada)bufo Th., (2) Nouvelles données sur la délétion portant sur le bras court d'unX chezMus (Leggada)triton Th

Summary The author treats 2 topics connected with his studies on the cytogenetics of the African pigmy-mice. (1)Mus (Leggada) bufo Th. shows the primitive complement already detected in other species or subspecies (minutoides ssp ₁,indutus, tenellus, setulosus): 2N=36,N.F.=36, sex chromosomesPR. (2) The deletion of the short arm of oneX-chromosome (X _dc ) was previously observed as heterozygous mutation by 4 in a sample of 7 and 5 . A more important sample (18 , 21 ) gives the following results: 11 X-X, 10 X-X _dc , 18 X-Y. The occurrence of X _dc -X _dc and of X _dc -Y is also very improbable. It is not easy to understand how the chromosomeX _dc may persist in the population if the complementsX _dc -X _dc andX _dc -Y are lethal, which seems to result from these observations.     

The mitochondrial processing peptidase: Function and specificity

Targeting signals of mitochondrial precursors are cleaved in the matrix during or after import by the mitochondrial processing peptidase (MPP). This enzyme consists of two nonidentical- and-subunits each of molecular weight of about 50 kDa. In mammals and fungi, MPP is soluble in the matrix, whereas in plants the enzyme is part of the cytochromebc ₁ complex. MPP is a metalloendopeptidase which has been classified as a member of the pitrilysin family on the basis of the HXXEHX₇₆E zinc-binding motif present in-MPP. Both subunits of MPP are required for processing activity. The-subunit of MPP, which probably recognizes a three-dimensional motif adopted by the presequence, presents the presequence to-MPP, which carries the catalytic active site. MPP acts as an endoprotease on chemically synthesized peptides corresponding to mitochondrial presequences. Matrix-targeting signals and MPP cleavage signals seem to be distinct, although the two signals may overlap within a given presequence. The structural element helix-turn-helix, that cleavable presequences adopt in a membrane mimetic environment, may be required for processing but is not sufficient for proteolysis. Binding of the presequence by-MPP tolerates a high degree of mutations of the presequence.-MPP may present a degenerated cleavage site motif to-MPP in an accessible conformation for processing. The conformation of mitochondrial presequences bound to MPP remains largely unknown.     

Levels ofα 1 in the spring and autumn seasons

Summary In a group of 84 pairs of 11-year-old children of both sexes, the level of the ₁-antitrypsin ( ₁-AT) were ascertained in the autumn and spring. Although the mean levels of ₁-AT in the two seasons hardly differed, the highly significant seasonal changes in the distribution curves of ₁-AT values were noted in boys, whereas the levels showed higher stability in girls.     

The presence and function of melatonin and structurally related indoleamines in a dinoflagellate,and a hypothesis on the evolutionary significance of these tryptophan metabolites in unicellulars

The bioluminescent dinoflagellateGonyaulax polyedra contains various indoleamines, in particular, melatonin and 5-methoxytryptamine, as well as enzymes of their biosynthetic pathway. Melatonin exhibits a high-amplitude circadian rhythm characterized by a dramatic increase shortly after the onset of darkness. The maximum of melatonin is followed by a peak of 5-methoxytryptamine. These 5-methoxylated indoleamines seem to be involved in the mediation of the information darkness.G. polyedra shows a short-day response, which consists in the formation of asexual cysts. Light break experiments demonstrate the photoperiodic nature of this reaction. Cells become sensitive to short days only upon exposure to a lowered temperature (<16°C). Melatonin mimics the short-day effect, but only at decreased temperature. 5-Methoxytryptamine is even a better inducer of cyst formation, acting also at 20°C and in any lighting schedule, including LL. Cyst induction is associated with stimulation of bioluminescence and cytoplasmic acidification. A model on the intracellular pathway of photoperiodic information transduction assumes increased deacetylation of melatonin under cyst-inducing conditions, binding of 5-methoxytryptamine to the membrane of an acidic vacuole, proton transfer to the cytoplasm, and decreased intracellular pH as the stimulus for encystment. Melatonin shows the property of a scavenger of superoxide anions. This reaction, which is efficiently catalyzed by hemin, leads to the formation of a substituted kynuramine (AFMK). Destruction of melatonin by light-induced superoxide anions in the presence of cellular hemin may represent a property which, during evolution, has made this molecule suitable as an indicator of darkness. On the other hand, AFMK, which is formed under illumination, might have become a mediator of the information light. Photoperiodism inGonyaulax shows surprising parallels to that in mammals, but allows the analysis of this phenomenon at an entirely cellular level.     

A lectin from the liverwortMarchantia polymorpha L

Bryophytes have been screened for lectins. From the liverwortMarchantia polymorpha (Marchiantiales) a lectin could be purified to homogeneity using a combination of ultrafiltration, size exclusion chromatography and ion exchange chromatography. SDS polyacrylamide gel electrophoresis, size exclusion chromatography and electrospray mass spectroscopy showed that the lectin is a monomeric protein with a M_r of 16,134.64 ± 2.93.Marchantia polymorpha lectin agglutinates erythrocytes of different mammalia and exhibits carbohydrate specifity against complex carbohydrate structures. This is the first report of a lectin isolated from liverworts.This article forms Publication No. 71 of the Arbeitskreis Biologie und Chemie der Moose.     

Nachweis der Bisulfit-Addukte (α-Oxysulfonsäuren) von Carbonylverbindungen in den mit SO2 behandelten Erbsenkeimlingen

Summary The intoxication of 15-day-old green pea seedlings with 1% gaseous SO₂ causes an important concentration fall of some free ketoacids (pyruvic, oxalacetic, -ketoglutaric) and of glyceraldehyde in the roots and shoots. This fall is a consequence of the reaction of these carbonyl compounds with SO₂ in the plant tissue under the formation of bisulphite adducts (-hydroxysulfonic acids), which have been chemically proved and quantitatively estimated.     

Vorgänge bei pH-Änderung und bei Belichtung eines Anthocyanidins

Summary The anthocyanidin investigated here exists below pH 4 as a cationAH ₂ ⁺ (wave length of absorption maximum _max=459 mµ), between pH 5 and 7 in the neutral formAH ( _max=492 mµ) and above pH 8 as an anionA ^– ( _max=537 mµ). At pH 5 the freshly dissolved substance is partially converted into a colourless formBH ( _max=372 mµ) and a chemical equilibrium betweenAH andBH is reached within 1 h. A kinetic study of the process of formation ofBH shows that an intermediate productZ is formed. This process can be reversed by light exposure. It can be concluded from a kinetic investigation by using flash light thatBH is transformed by the absorbing light into a new substanceL ( _max 275 mµ and 225 mµ), andL changes partially intoBH, partially intoZ, which itself is transformed partially intoAH ₂ ⁺ ,AH,A ^–, partially intoBH. The reactionZ AH,AH ₂ ⁺ ,A ^– is proportional to the concentration of protons [H ⁺], the reactionZ BH independent of [H ⁺]. Thus a photochemical production ofAH ₂ ⁺ ,AH,A ^– fromBH is readily obtained in the presence ofH ⁺ and not obtained in the absence ofH ⁺.     

Nouvelles données sur la cytogénétique et la spéciation des Leggada (Mammalia-Rodentia-Muridae)

Summary To the 237 pigmy-mice studies in his previous papers, the author brings new data concerning the cytogenetics of 25 Leggada. One first set of 12 mice from Nigeria belongs to the same polymorphic series containing themusculoides from the Ivory Coast and the Central African Republic.A small sample from Ippy (Central African Republic), although the individuals are morphologically all alike and referable tomusculoides, shows an amazing diversity: /259.2N=28, N.F.=36, sex chromosomes of the translocated type (TR). We meet here a new robertsonian combination in the polymorphic series, 34/33/32/31 ... 28/... 22/... 19/18./260.2N=32, N.F.=36, sex chromosomesTR. Both big biarmed autosomes are metacentric — submetacentric with a centromeric index of about 0.25 by the typicalmusculoides having the same diploid number./261.2N=19, N.F.=36, sex chromosomesX/Y ₁ Y ₂. The first occurrence of such sex chromosomes by the Leggada. By themusculoides from Rhodesia we were dealing with the typeX ₁ X ₂ /Y. /262.2N=18, N.F.=36, sex chromosomesX/X. Very likely the female of /261.In the complexminutoides-musculoides, we meet many different caryotypes and it is obvious that the chromosomal mutations play here the part of a primary factor of isolation, previous to the gene mutations which later will allow the taxonomic determination of the species actually in statu nascendi.     

Thermodynamics of bromate and iodate of sodium in dioxane-water mixtures at different temperatures

Summary The free energy transfer (G _t ⁰ ) enthalpy of transfer (H _t ⁰ ) and entropy of transfer (S _t ⁰ ) of NaBrO₃ and NaIO₃ from water to 10, 20 and 30% dioxane-water mixtures have been studied using conductance measurements. The chemical and electrical parts of these transfers of thermodynamic parameters have been estimated.To whom reprint requests should be addressed.     

Comparative analysis of human milk and human blood plasma by means of diffusion-in-gel methods

Zusammenfassung Mit Hilfe von Immunoelektrophorese und Doppeldiffusiontechnik wurden in Humanmilch an Blutplasmaproteinen serologisch identifiziert: Praealbumin, Albumin, Acid Seromucoid, ₁-Glykoprotein (3·5 S), Coeruloplasmin, Haptoglobin, ₂- oder-Lipoprotein, Transferrin, Fibrinogen, _2A-Globulin, _2M-Globulin und-Globulin.     

The biosynthesis of trisporic acids fromβ-carotene via retinal and trisporol

Zusammenfassung AusBlakeslea trispora wird eine neue Verbindung, Trisporol-C isoliert, ihre Struktur aufgeklärt und die Biosynthese der verwandten Trisporinsäuren aus-Carotin und retinal untersucht.