ESR and ENDOR of primary reactants in photosynthesis

The primary reactants in photosynthesis are defined as the chemical entities on which charges are generated and stabilized after capture of a photon by the photochemical trap: PIX ^hv P ^* IX P ⁺ I ^– X P ⁺ IX ^–, where P stands for the primary electron donor, P ^* for its excited singlet state, I for the first (ESR-detectable) electron acceptor and X for the secondary acceptor complex. The ESR and ENDOR experiments which have played a rÔle in the identification and characterization of P, I, and X in the bacterial and plant photosystems are comprehensively reviewed. The structural and kinetic information obtained with magnetic resonance techniques are integrated with results obtained with optical spectroscopy to give a unified picture of the pathway of primary photochemistry in photosynthesis. Nomenclature of Primary Reactants In the interest of uniformity this review introduces a nomenclature of the primary reactants that deviates in some respects from the commonly used labels. The nametags used here and listed below are abbreviations of the molecules that are identified as primary reactants, with the exception of the donors, for which I have retained the commonly accepted designation. Photosystems: PS 1, photosystem 1 of plants; PS 2, photosystem 2 of plants; pBPS, the photosystem of purple bacteria; gBPS, ditto of green bacteria. P: Primary donors: P700 (PS 1), P680 (PS 2), P860 (generic label for BChl a containing purple bacteria), P960 (generic label for BChl b containing purple bacteria), P840 (generic name for green bacteria). I: First acceptors: Chl a (PS 1), Ph a (PS 2), BPh a,b (pBPS). X: Secondary acceptors: F _x (PS 1), pQ ₁ (PS 2), uQ ₁ or mQ ₁ (pBPS), B (gBPS). Tertiary acceptors: F _A,B (PS 1), pQ ₂ (PS 2), uQ ₂ (pBPS), F ₁ (gBPS).This paper is based on a lecture given at the Joint Meeting of the Belgium, German (FRG), and Netherlands Societies for Biophysics, Aachen 1980     

Solubilization and partial purification of protein kinase systems from brain membranes that phosphorylate calspectin: A spectrin-like calmodulin-binding protein (fodrin)

In brain tissue a spectrin-like calmodulin-binding protein calspectin, or fodrin, is concentrated in a synaptosome fraction, where most of the calspectin is associated with the synaptic membranes. This endogenous calspectin was phosphorylated by protein kinase system(s) associated with the membranes. Here, we report the solubilization and partial purification of the membrane-associated calspectin kinase activity. The activity was resolved on a gel filtration column into two fractions, peaks I and II having estimated M_r of 800 000 and 88 000. The activity of peak I was dependent on the presence of both Ca²⁺ and calmodulin. Peak II revealed a basal activity in the absence of Ca²⁺ and calmodulin, which was stimulated 2-fold by addition of Ca²⁺. Calmodulin had no effect on the peak II activity.     

Increased Noradrenergic Metabolism in the Cerebellum of the Mouse Mutant Dystonia Musculorum

Abstract: The neurological mouse mutant dystonia musculorum exhibits bizarre appendicular and truncal dystonia without known cerebellar histopathology. We evaluated striatal dopamine and cerebellar norepinephrine metabolism in this mutant and compared the results with those obtained in wild-type BALB/c and B6C3 controls. Tyrosine hydroxylase activity and dopamine metabolite levels (homovanillic acid and 3,4-dihydroxyphenylacetic acid) in the striatum of the mutant were similar to controls. Tyrosine hydroxylase activity and the steady-state level of 3-methoxy-4-hydroxyphenethyleneglycol, a metabolite of norepinephrine, in the cerebellum were 38% and 42-66%, respectively, greater in the mutant. However, the level of norepinephrine was similar (∼350 ng/g). Further, a Purkinje cell-specific marker, cGMP-dependent protein kinase, was unchanged in the mutant and no Purkinje cell pathology was observed with light microscopy. The lack of Purkinje cell derangement and similar levels of cerebellar norepinephrine and cGMP-dependent protein kinase activity suggest that increased norepinephrine metabolism in the cerebellum of this mutant is not a morphological response to gross target cell loss during morphogenesis. The observed changes may be a reaction to abnormal impulse traffic or altered input/output pathways to the mutant cerebellum during its development.     

Activation of Retinal Tyrosine Hydroxylase In Vitro by Cyclic AMP-Dependent Protein Kinase: Characterization and Comparison to Activation In Vivo by Photic Stimulation

Abstract: Tyrosine hydroxylase in rat retina is activated in vivo as a consequence of photic stimulation. Tyrosine hydroxylase in crude extracts of dark-adapted retinas is activated in vitro by incubation under conditions that stimulate protein phosphorylation by cyclic AMP-dependent protein kinase. Comparison of the activations of the enzyme by photic stimulation in vivo and protein phosphorylation in vitro demonstrated several similarities. Both treatments decreased the apparent K _m of the enzyme for the synthetic pterin cofactor 6MPH₄. Both treatments also produced the same change in the relationships of tyrosine hydroxylase activity to assay pH. When retinal extracts containing tyrosine hydroxylase activated either in vivo by photic stimulation or in vitro by protein phosphorylation were incubated at 25°C, the enzyme was inactivated in a time-dependent manner. The inactivation of the enzyme following both activation in vivo and activation in vitro was partially inhibited by sodium pyrophosphate, an inhibitor of phosphoprotein phosphatase. In addition to these similarities, the activation of tyrosine hydroxylase in vivo by photic stimulation was not additive to the activation in vitro by protein phosphorylation. These data indicate that the mechanism for the activation of tyrosine hydroxylase that occurs as a consequence of light-induced increases of neuronal activity is similar to the mechanism for activation of the enzyme in vitro by protein phosphorylation. This observation suggests that the activation of retinal tyrosine hydroxylase in vivo may be mediated by phosphorylation of tyrosine hydroxylase or some effector molecule associated with the enzyme.     

Genetic analysis of transpositions in the lac region of Escherichia coli

The lac region of Escherichia coli, carried on an F′ lacproB episome, was used as a target for the transposition of several transposable elements. Tn9 shows a preferential integration (by a factor of 50) into a region extending from the end of the Z gene through the Y gene. Throughout the remainder of the lacI, Z and Y genes one other short region, located in the middle of the I gene, is favored for integration. Within these favored regions many different integration points are evident. Inspection of the DNA sequence for the I and Y genes, and parts of the Z gene, shows a strong correlation between A + T richness and regions of preferential integration. Tn5 insertions follow a similar pattern, although with less preference; whereas Tn10 insertions (provided by T. J. Foster), also favor the Y gene and the end of Z, but are distributed among fewer integration points. Most of the Tn3 insertions into the episome are accompanied by a nearby or adjacent deletion.     

High resolution two-dimensional gel electrophoresis of the proteins and glycoproteins of human blood platelets and platelet membranes

The proteins and glycoproteins of human blood platelets and platelet membranes in both the reduced and the unreduced states have been analysed by isoelectric focusing and sodium dodecyl sulphate-discontinuous polyacrylamide gel electrophoresis in a two-dimensional technique. Gels which had been stained with periodic acid-Schiff's reagent could be counter-stained with Coomassie Brilliant Blue, simplifying the recognition of components which stain with both reagents. The major glycoproteins and some of the proteins have been identified and the characteristics of the membrane and of the whole platelet components established in this system.     

Growth yields and the efficiency of oxidative phosphorylation of Paracoccus denitrificans during two- (carbon) substrate-limited growth

Paracoccus denitrificans was grown aerobically during two-(carbon)substrate-limitation on mannitol and methanol in chemostat cultures. Theoretical growth parameters were calculated based on the presence of 2 or 3 sites in the electron-transport chain of Paracoccus denitrificans. Experimental growth parameters determined during two-(carbon)substrate growth were conform to the presence of 3 sites of oxidative phosphorylation, while cells grown only on mannitol possessed 2 sites. The maximum growth yield on adenosine triphosphate (ATP), corrected for maintenance requirements, determined in chemostat experiments in which the methanol concentration is less than 2.11 times the mannitol concentration was 8.6 g of biomass. When the methanol concentration was more than 2.11 times the mannitol concentration the maximum growth yield on adenosine triphosphate decreased due to the more energy consuming process of CO₂-assimilation. Cells use methanol only as energy source to increase the amount of mannitol used for assimilation purposes. When the methanol concentration in chemostat experiments was more than 2.11 times the mannitol concentration, all mannitol was used for assimilation and excess energy derived from methanol was used for CO₂-assimilation via the ribulose-bisphosphate cycle. The synthesis of ribulosebisphosphate carboxylase was repressed when the methanol concentration in chemostat experiments was less than 2.11 times the mannitol concentration or when Paracoccus denitrificans was grown in batch culture on both methanol and mannitol. When in chemostat experiments the methanol concentration was more than 2.11 times the mannitol concentration ribulose-bisphosphate carboxylase activity could be demonstrated and CO₂-assimilation will occur. It is proposed that energy produced in excess activates or derepresses the synthesis of the necessary enzymes of the ribulose-bisphosphate cycle in Paracoccus denitrificans. Consequently growth on any substrate will be carbonas well as energy-limited. When methanol is present in the nutrient cells of Paracoccus denitrificans synthesize a CO-binding type of cytochrome c, which is essential for methanol oxidase activity.The reason for the increase in efficiency of oxidative phosphorylation from 2 to 3 sites is most probably the occurrence of this CO-binding type of cytochrome c in which presence electrons preferentially pass through the a-type cytochrome region of the electron-transport chain.Non Standard Abbreviations X prosthetic group of methanol dehydrogenase - q _substrate specific rate of consumption of substrate (mol/g biomass. h.) - Y _substrate, Y _substrate ^MAX are respectively the growth yield and the maximum growth yield corrected for maintenance requirements (g biomass/mol) - m _substrate maintenance requirement (mol substrate/g biomass) - specific growth rate (h^-1) - M [methanol]/[mannitol] ratio in the nutrient - N part of mannitol that is assimilated when M=o - R _m amount of methanol-equivalents that has the same energy content as 1 mannitol-equivalent - P/O _N , P/O _F , P/O _X is the amount of ATP produced during electron-transport of two electrons from respectively NADH+H⁺, FADH₂ and XH₂ to oxygen     

NMR of fd coat protein

The conformations of the major coat protein of a filamentous bacteriophage can be described by nuclear magnetic resonance spectroscopy of the protein and the virus. The NMR experiments involve detection of the ¹³C and ¹H nuclei of the coat protein. Both the ¹³C and ¹H nuclear magnetic resonance (NMR) spectra show that regions of the polypeptide chain have substantially more motion than a typical globular protein. The fd coat protein was purified by gel chromatography of the SDS solubilized virus. Natural abundance ¹³C NMR spectra at 38 MHz resolve all of the nonprotonated aromatic carbons from the three phenylalanines, two tyrosines, and one tryptophan of the coat protein. The α carbons of the coat protein show at least two different classes of relaxation behavior, indicative of substantial variation in the motion of the backbone carbons in contrast to the rigidity of the α carbons of globular proteins. The ¹H spectrum at 360 MHz shows all of the aromatic carbons and many of the amide protons. Titration of a ¹H spectra gives the pKas for the tyrosines.     

Cytological changes and DNA and protein synthesis in parthenogenetically activated sea urchin eggs

Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of³H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the³H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the³H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of¹⁴C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction.     

Ferritin as an exogenous yolk protein in snails

Summary A main yolk component in the oocytes of the pulmonate snailPlanorbarius corneus L. has been isolated and identified as the iron storage protein ferritin by its ultrastructure, iron content, immuunological properties and behaviour in disc electrophoresis. As judged from acrylamide electrophoresis data and ultrastructural observations, yolk ferritin is an exogenous protein which is synthesised in the hepatopancreas and taken up by the oocytes by endocytosis.