Reconstitution of acetylcholine receptor from Torpedo californica with highly purified phospholipids: Effect of α-tocopherol,phylloquinone, and other terpenoid quinones

Acetylcholine receptor from $\text{Torpedo californica}$ can be incorporated by the cholate dialysis procedure into liposomes prepared with crude soybean phospholipids (asolectin). Vesicles reconstituted with asolectin depleted of neutral lipids or with a mixture of pure phospholipids, are less active in catalyzing carbamylcholine-sensitive Na⁺ flux. Inclusion of α-tocopherol or certain quinones such as coenzyme Q₁₀ or vitamin K₁ during reconstitution yields vesicles with carbamylcholine-sensitive Na⁺ flux which, under optimal conditions, was considerably higher than that observed with vesicles reconstituted with crude phospholipid mixtures.     

Genetic polymorphism of the major parotid salivary glycoprotein (Gl) with linkage to the genes for Pr,Db, and Pa

Genetic polymorphism of the major glycoprotein (Gl) found in parotid saliva is determined by autosomal inheritance of one unexpressed and four expressed alleles. This hypothesis is supported by studies in 41 white families including 146 children. For 143 randomly collected salivas from whites and 82 randomly collected salivas from blacks, maximum likelihood estimates of the gene frequencies are as follows: for whites, Gl ¹=0.742, Gl ²=0.040, Gl ³=0.155, Gl ⁴=0.017, Gl ⁰=0.046; for blacks, Gl ¹=0.459, Gl ²=0.050, Gl ³=0.337, Gl ⁴=0.044, Gl ⁰=0.110. There is strong evidence for linkage of Gl/Pr (seven families, lod score at =0 is 5.24) and Gl/Db (eight families, lod score at =0 is 4.45). The allelic products of Gl show evidence for linkage disequilibrium with the products of the Pr, Db, and Pa loci (P<0.0005). On the basis of varying degrees of linkage disequilibrium, Gl may be closer to Db than to Pr or Pa and on the outside of Db with respect to Pr or Pa. Amino acid analyses of Gl 1 and Gl 4 proteins show strong resemblances in composition to the major basic glycoprotein and the acidic proline-rich proteins of parotid saliva described by other workers. The polymorphic forms of the Gl proteins show microheterogeneity due to variability in charge and molecular weight. The electrophoretic polymorphism appears to be determined by apparent differences in molecular weights between the Gl proteins.This study was supported by a grant from the National Institutes of Dental Research (DEO 3658-12) and in part by NIH Grant GM 15422 and NIH Training Grant GM 00398. Paper No. 2242 of the Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706.     

ULTRASTRUCTURE OF GLANDULAR TRICHOMES OF LEAVES OF NICOTIANA TABACUM L., cv XANTHI

Electron microscopy confirms previous light microscope observations that tobacco leaf trichomes are glandular and that there are two different types. Both the tall trichome (multicellular stalk, unicellular or multicellular head) and the short trichome (unicellular stalk; multicellular head) exhibit characteristics common to gland cells—a dense cytoplasm, numerous mitochondria, and little vacuolation. The tall trichome contains structurally well developed chloroplasts and an elaborate network of endoplasmic reticulum. The short trichome contains undifferentiated plastids and endoplasmic reticulum which parallels the nucleus and plasmalemma. Few dictyosomes are seen either in the short trichome or in the tall trichome. The short trichome appears to undergo structural changes concurrently with the appearance of secretory product within the cells. The most noticeable change is the formation of the extraplasmic space between the cell wall and the plasmalemma. Electron dense secretory product is observed between the plasmalemma and the cell wall and within the intercellular spaces.     

ATP synthesis in a succinate decarboxylase system from Fasciola hepatica mitochondria

Köhler P. B.,Ryant C. and Behm Carolyn A. 1978. ATP synthesis in a succinate decarboxylase system from Fasciola hepatica mitochondria. International Journal for Parasitology8: 399–404. Succinate decarboxylation was measured by the formation of ¹⁴CO₂ from 1,4-¹⁴C-succinate in a particle free, dialysed mitochondrial extract from liver fluke. It has an absolute requirement for Mg²⁺ and CoA. ATP, ADP and inorganic phosphate are essential for optimal activity. Ap₅A, an inhibitor of adenylate kinase, and glutathione are also necessary. GTP supports decarboxylation as well as ATP, provided ADP is also present. The formation of CO₂ and propionate greatly exceeds the amount of ATP and CoA initially present in the reaction mixture. A net, substrate-level phosphorylation of ADP occurs, the amount of ATP formed being equivalent to the production of CO₂ or propionate. This system is inhibited in flukes incubated in vitro with mebendazole.It is concluded that ATP is required to spark the fermentation system when succinate is the initial substrate and intermediate substrates are absent; that the terminal step in propionate formation is catalysed by a transferase which transfers CoA from propionyl CoA to succinate; and that ATP formation is coupled to the decarboxylation of methylmalonyl-CoA. A reaction scheme is presented.     

Kinetics and morphology of glucose-limited cultures of moulds grown in a chemostat and on solid media

The affinity (K _s value) of Geotrichum candidum for glucose determined from chemostat cultures was ca. 1 mg/l. K _s values for glucose were also estimated from the radial growth rates of colonies of G. candidum and Neurospora crassa grown on media solidified with agar or silica gel. An assessment is made of the use of colony radial growth rate to determine substrate affinities. The length of apical and intercalary hyphal comparte ments, internode length and the diameter of leading hyphaat the margin of colonies grown on solid media were all reduced at low glucose concentrations.     

Crystals of modified fibrinogen: Size,shape and packing of molecules

We have produced several new macroscopic crystal forms and a variety of microcrystals from modified flbrinogens. Bovine and rabbit flbrinogens crystallize after limited digestion by a bacterial protease or α-chymotrypsin. The fibrinogens making up these crystals are largely intact and highly clottable. Tentative molecular packing arrangements for two crystal forms have been deduced. The crystal morphology and cleavage planes were used in this analysis. The characteristic α-helical coiled-coil reflections arid spikes of intensity in certain directions in the crystal X-ray patterns serve as markers for the orientation of the fibrinogen molecules. Changes that occur in one of the forms during preparation for electron microscopy, as shown by comparison with X-ray experiments on crystals in various stains and solvents, support this packing model. These studies provide preliminary evidence that fibrinogen is about 450 Å in length and that the molecules bond end-to-end to form filaments making up the crystals.