Involvement of the molecular chaperone BiP in maturation of Sindbis virus envelope glycoproteins.

Sindbis virus codes for two membrane glycoproteins, E1 and PE2, which assemble into heterodimers within the endoplasmic reticulum. We have examined the role of the molecular chaperone BiP (grp78) in the maturation of these two proteins. E1, which folds into its mature conformation via at least three intermediates differing in the configurations of their disulfide bonds, was found to interact strongly and transiently with BiP after synthesis.

Polar distribution of annexin-like proteins during phytochrome-mediated initiation and growth of rhizoids in the ferns Dryopteris and Anemia.

Although the calcium requirement of phytochrome-mediated fern spore germination and early rhizoid growth is well established, the calcium-binding proteins that serve as transducers for these responses are not known. Here we report the presence of annexin-like proteins in germinating spores of Dryopteris filix-mas (L.) Schott and Anemia phyllitidis (L.

Partial purification and characterization of an enzyme from pea nuclei with protein tyrosine phosphatase activity.

A pea (Pisum sativum L.) nuclear enzyme with protein tyrosine phosphatase activity has been partially purified and characterized. The enzyme has a molecular mass of 90 kD as judged by molecular sieve column chromatography and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

The configuration of Sindbis virus envelope proteins is stabilized by the nucleocapsid protein.

We have previously provided evidence that a strong and precise interaction of the Sindbis virus nucleocapsid with the cytoplasmic tail of E2 is critical for the function of the mature virion and that changes in this association may affect infectivity (21). In this study, we examined the effects of temperature-sensitive defects in capsid protein on virus infectivity and glycoprotein function. The two Sindbis virus mutants chosen were ts2 and Ser180/Gly183, which contain amino acid substitutions in their capsid proteins.

Control of lhc gene transcription by the circadian clock in Chlamydomonas reinhardtii.

Transcription of nuclear lhc genes has been shown to be under circadian clock control in angiosperms. but many aspects of this regulation have not been elucidated. Unicellular organisms, such as the green alga Chlamydomonas reinhardtii, offer significant advantages for the study of cellular clocks.

Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization.

The synthesis of an extracellular ribbon of cellulose in the bacterium Acetobacter xylinum takes place from linearly arranged, membrane-localized, cellulose-synthesizing and extrusion complexes that direct the coupled steps of polymerization and crystallization. To identify the different components involved in this process, we isolated an Acetobacter cellulose-synthesizing (acs) operon from this bacterium. Analysis of DNA sequence shows the presence of three genes in the acs operon, in which the first gene (acsAB) codes for a polypeptide with a molecular mass of 168 kDa, which was identified as the cellulose synthase.

Deficient nucleation during co-polymerization of mammalian MAP2 and tobacco tubulin.

To obtain information on the functional domains of tubulin from a dicot plant, we investigated the interactions of tobacco tubulin with MAP2 from bovine brain supernatant. Taxol-stabilized tobacco and bovine brain microtubules had similar binding capacities for MAP2 (1 mol MAP2 per 8-9 mol tubulin). However, MAP2 dissociated from tobacco microtubules more readily than from bovine brain microtubules and induced the polymerization of tobacco tubulin into aberrant helical ribbon polymers, rather than microtubules.

Mutations in an exposed domain of Sindbis virus capsid protein result in the production of noninfectious virions and morphological variants.

A critical event in the process of Sindbis virus assembly is the interaction of the virus nucleocapsid with the target membrane which has been modified by virus envelope glycoproteins. A specific association between the endodomain of the pE2/E2 glycoprotein and an unidentified domain in the capsid protein is responsible for this association. We have examined the nature of this association by the production of a mutant which has two amino acid substitutions in a domain of the capsid protein known to be exposed on the surface of the assembled nucleocapsid (Ser180/Gly183).

An acylated flavone C-glycoside from Glycyrrhiza eurycarpa.

A new acylated flavone C-glycoside, apigenin 6-C-alpha-L-rhamnopyranoside-8-C-[6"-(3-hydroxy-3-methyl-glutaroyl )-beta-D-glucopyranoside], was isolated from rhizomes of Glycyrrhiza eurycarpa and its structure was established on the basis of spectroscopic data.

Flavonol glycosides from Cephalocereus senilis.

A new flavonol tetraglycoside, together with two known flavonol glycosides, kaempferol 7-rhamnoside and kaempferol 3-rhamnosyl(1-->6) galactoside-7-rhamnoside, were isolated from fresh plant material of Cephalocereus senilis. The structure of the new compound was established as kaempferol 3-O-beta-D-glucopyranosyl(1-->2)-O-[alpha-L-rhamnopyranosyl (1-->6)]-beta-D-galactopyranoside-7-O-alpha-L-rhamnopyranoside based on spectroscopic data. The whole plant flavonoid chemistry was strikingly different from that found previously in chitin-treated cell suspension cultures of the same plant.

A 55-kDa protein induced in Aedes albopictus (mosquito) cells by antiviral protein.

We have previously shown that the antiviral protein (AVP) produced by Sindbis virus-infected Aedes albopictus (mosquito) cells (Riedel and Brown, J. Virol. 29, 51-60, 1979) blocks Sindbis viral RNA synthesis and stimulates its own production when applied to uninfected A.

A chloroplast group I intron undergoes the first step of reverse splicing into host cytoplasmic 5.8 S rRNA. Implications for intron-mediated RNA recombination, intron transposition and 5.8 S rRNA structure.

The chloroplast 23 S rRNA gene of Chlamydomonas reinhardtii contains a self-splicing group I intron, Cr.LSU. Incubation of total RNA from C.

Formation and rearrangement of disulfide bonds during maturation of the Sindbis virus E1 glycoprotein.

The rigidly ordered icosahedral lattice of the Sindbis virus envelope is composed of a host-derived membrane bilayer in which the viral glycoproteins E1 and E2 reside. E1-E1 interactions stabilized by intramolecular disulfide bridges play a significant role in maintaining the envelope's structural integrity (R. P.

Limited period of graviresponsiveness in germinating spores of Ceratopteris richardii.

Rhizoids of the fern Ceratopteris richardii Brogn. usually emerge 40 h after germination is initiated by light, and more than 90% of them emerge growing in a downward direction. However, when the spores are germinated on a clinostat, the emerging rhizoids show no preferential orientation.

Three-dimensional structure of a membrane-containing virus.

The structure of Sindbis virus was determined by electron cryomicroscopy. The virion contains two icosahedral shells of viral-encoded proteins separated by a membrane bilayer of cellular origin. The three-dimensional structure of the ice-embedded intact Sindbis virus, reconstructed from electron images, unambiguously shows that proteins in both shells are arranged with the same icosahedral lattice of triangulation number T = 4.

Phosphorylation and dephosphorylation events play critical roles in Sindbis virus maturation.

We have examined the effects of various inhibitors of protein kinases and phosphatases on Sindbis virus maturation in BHK cells. 2-aminopurine, a nonspecific protein kinase inhibitor, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), a specific inhibitor of calmodulin/Ca(2+)-dependent protein kinase, and okadaic acid (OKA), a protein phosphatase inhibitor, dose-dependently inhibited Sindbis virus maturation. Although virus production was inhibited, the membrane glycoprotein precursors PE2/E1 were exported from the endoplasmic reticulum and PE2 was converted to E2 at normal kinetic rates.

Unique functional characteristics of the polymerization and MAP binding regulatory domains of plant tubulin.

An understanding of the regulation of microtubule polymerization and dynamics in plant cells requires biochemical information on the structures, functions, and molecular interactions of plant tubulin and microtubule-associated proteins (MAPs) that regulate microtubule function. We have probed the regulatory domain and polymerization domain of purified maize tubulin using MAP2, an extensively characterized mammalian neuronal MAP. MAP2 bound to the surface of preformed, taxol-stabilized maize microtubules, with binding saturation occurring with one MAP2 molecule per five to six tubulin dimers, as it does with mammalian microtubules.

The major nucleoside triphosphatase in pea (Pisum sativum L.) nuclei and in rat liver nuclei share common epitopes also present in nuclear lamins.

The major nucleoside triphosphatase (NTPase) activities in mammalian and pea (Pisum sativum L.) nuclei are associated with enzymes that are very similar both biochemically and immunochemically. The major NTPase from rat liver nuclei appears to be a 46-kD enzyme that represents the N-terminal portion of lamins A and C, two lamina proteins that apparently arise from the same gene by alternate splicing.

Purification and characterization of a casein kinase 2-type protein kinase from pea nuclei.

Almost all the polyamine-stimulated protein kinase activity associated with the chromatin fraction of nuclei purified from etiolated pea (Pisum sativum L.) plumules is present in a single enzyme that can be extracted from chromatin by 0.35 molar NaCl.

Partial purification and characterization of a Ca(2+)-dependent protein kinase from pea nuclei.

Almost all the Ca(2+)-dependent protein kinase activity in nuclei purified from etiolated pea (Pisum sativum, L.) plumules is present in a single enzyme that can be extracted from chromatin by 0.3 molar NaCl.

Partial purification and characterization of a Ca(2+)-dependent protein kinase from the green alga, Dunaliella salina.

A calcium-dependent protein kinase was partially purified and characterized from the green alga Dunaliella salina. The enzyme was activated at free Ca2+ concentrations above 10(-7) molar. and half-maximal activation was at about 3 x 10(-7) molar.

Phytochrome induces changes in the immunodetectable level of a wall peroxidase that precede growth changes in maize seedlings.

The regulatory pigment phytochrome induces rapid and opposite growth changes in different regions of etiolated maize seedlings: it stimulates the elongation rate of coleoptiles and inhibits that of mesocotyls. As measured by a quantitative immunoassay, phytochrome also promotes rapid and opposite changes in the extractable content of a Mr 98,000 anionic isoperoxidase in the cell walls of these same organs: it induces a decrease of this peroxidase in coleoptiles and an increase in mesocotyls. The peroxidase changes precede the growth changes.