Metal ion requirements and other aspects of the reaction catalyzed by M1 RNA, the RNA subunit of ribonuclease P from Escherichia coli

M1 RNA, the RNA subunit of ribonuclease P from Escherichia coli, can under certain conditions catalytically cleave precursors to tRNA in the absence of C5, the protein moiety of RNase P. M1 RNA itself is not cleaved during the reaction, nor does it form any covalent bonds with its substrate. Only magnesium and, to a lesser extent, manganese ions can function at the catalytic center of M1 RNA. Several other ions either inhibit the binding of magnesium ion at the active site or function as structural counterions. The reaction rate of cleavage of precursors to tRNAs by M1 RNA is enhanced in the presence of poly-(ethylene glycol) or 2-methyl-2,4-pentanediol. Many aspects of the reaction catalyzed by M1 RNA are compatible with a mechanism in which phosphodiester bond cleavage is mediated by metal ion.     

The repetitive structure of the profilaggrin gene as demonstrated using epidermal profilaggrin cDNA

Filaggrin is the histidine-rich basic protein that aggregates keratin filaments in fully differentiated cells of the epidermis. Filaggrin is synthesized in the granular cell layer as a high molecular weight precursor protein (profilaggrin) that consists of multiple repeated copies of filaggrin. cDNA clones for rat and mouse epidermal profilaggrin have been constructed from sucrose gradient-enriched RNA in order to study the repetitive structure of profilaggrin. These clones hybridize to high molecular weight epidermal mRNA (23 kilobase pairs, rat and 19 kilobase pairs, mouse) and exhibit limited cross-hybridization between species. Several rat clones direct the synthesis of a portion of rat profilaggrin in bacteria. One of these, rat profilaggrin cDNA clone R4D6, is 2400 base pairs in length. The R4D6 cDNA is shown to contain repetitive sequence by restriction mapping and southern hybridization analysis of restriction digests of this plasmid, using subfragments of the plasmid as hybridization probes. Southern hybridization analysis of rat genomic DNA, digested to completion with several restriction enzymes, reveals a simple hybridization pattern of fragments equal in size to those of the cDNA. Partial digestion of rat genomic DNA results in a ladder of bands based on a 1200-base pair repeat, equal to the size of the repeating unit of the cDNA clone, and consistent with the expected repeating size of profilaggrin. Together, these results show that the profilaggrin mRNA and gene have repetitive structure and that the gene apparently lacks introns in the coding region.     

Characterization of the human epidermal profilaggrin gene. Genomic organization and identification of an S-100-like calcium binding domain at the amino terminus.

Filaggrin is an intermediate filament-associated protein which functions to aggregate keratin intermediate filaments in the stratum corneum of mammalian epidermis. It is synthesized as a large precursor protein, profilaggrin, that consists of multiple filaggrin units and is localized in keratohyalin granules. In this report, we describe the characterization of cosmid genomic clones containing the human profilaggrin gene coding for 11 complete filaggrin repeats of 324 amino acids each. At the amino- and carboxyl-terminal ends of human profilaggrin are leader and tail peptide sequences of 293 and 157 amino acids, respectively, which differ from filaggrin. The leader peptide is composed of two distinct domains: an 81-residue segment which shows significant homology to the S-100 family of EF hand-containing calcium-binding proteins, and a hydrophilic second domain of 212 residues. The gene is divided into three exons, with one intron (approximately 9.6 kilobase pairs) in the 5' noncoding region and a second one of 570 base pairs between the EF hands. The position of intron 2 is identical to that of other members of the S-100-like family. The presence of an S-100-like domain suggests that profilaggrin binds calcium and that the calcium binding domain is functionally significant in the formation of keratohyalin and/or the subsequent processing of profilaggrin to filaggrin, both of which may be calcium-dependent events.     

The relation between nitrogen percent and dry weight of inoculated legumes

Summary Results of numerous tests of tropical and temperate legume hosts and Rhizobium strains accumulated between 1952 and 1966 were examined for a relation between N percent (y) and dry weight per plant (x). The data fitted the equation y=A–be^–cx. The most effective Rhizobium strains can be selected on the basis of dry matter yields of whole plants or plant tops only, without the need for N analyses, using statistical analyses. A previously proposed method which employs the linear relation between N-yield and dry matter yield was shown to apply only when data for strains which are not fully effective are excluded.It is postulated that symbiotically fixed N forms a different compound from that resulting from applied mineral N and that this compound cannot be remobilised before flowering.deceased     

A STUDY OF THE CINNAMON-BREASTED ROCK BUNTING Fringillaria tahapisi tehepisi

Brown, C. J. &; Piper, S. E. 1988. Status of Cape Vultures in the Natal Drakensberg and their cliff site selection. Ostrich 59:126-136.

Ground, aerial and questionnaire surveys on the status of the Cape Vulture Gyps coprotheres in the Little and High Drakensberg mountain ranges of Natal were carried out from 1981–1983. The area supported at least 1325 Cape Vultures, 60% on the High Drakensberg in 17 nesting colonies (mean of 31 birds per colony) and 38 roosts (mean of 7 birds). In the Little Drakensberg 17 sites were found, six of which were confirmed nesting colonies (mean of 53 birds) and seven were roosts (mean of 16 birds). A minimum of 215 nests was recorded while the actual number of breeding pairs was probably about 325. In the Natal Drakensberg 84% of nests and 77% of roosting birds occupied ledges that faced between east and south, on the lee side of the generally westerly and northwesterly “Bergwind”. Nesting ledges in the High Drakensberg were on average about 100 m lower than roosting ledges. The northern Drakensberg supported the largest numbers of Cape Vultures (19 birds per 10 km of cliffs), while the smallest numbers were recorded in the south (8 birds per 10 km of cliffs). In the south smallstock farming predominates and the availability of carrion is higher than in the north where mainly largestock are farmed. The use of poisons (mainly strychnine) for killing mammalian predators on farms is considered to be the main reason for fewer birds occurring in the south, and is the main threat to Cape Vultures in the Natal Drakensberg.     

Biosynthesis of Dictyostelium discoideum differentiation-inducing factor by a hybrid type I fatty acid-type III polyketide synthase

Differentiation-inducing factors (DIFs) are well known to modulate formation of distinct communal cell types from identical Dictyostelium discoideum amoebas, but DIF biosynthesis remains obscure. We report complimentary in vivo and in vitro experiments identifying one of two approximately 3,000-residue D. discoideum proteins, termed 'steely', as responsible for biosynthesis of the DIF acylphloroglucinol scaffold. Steely proteins possess six catalytic domains homologous to metazoan type I fatty acid synthases (FASs) but feature an iterative type III polyketide synthase (PKS) in place of the expected FAS C-terminal thioesterase used to off load fatty acid products. This new domain arrangement likely facilitates covalent transfer of steely N-terminal acyl products directly to the C-terminal type III PKS active sites, which catalyze both iterative polyketide extension and cyclization. The crystal structure of a steely C-terminal domain confirms conservation of the homodimeric type III PKS fold. These findings suggest new bioengineering strategies for expanding the scope of fatty acid and polyketide biosynthesis.     

Enhancement of the efficacy of a carbamate nematicide against the potato cyst nematode, Globodera pallida, through mycorrhization in commercial potato fields

Two experiments were conducted over 2 years in commercial potato fields in Shropshire, UK, to evaluate the compatibility of the nematicide aldicarb with commercial inocula of arbuscular mycorrhizal fungi (AMF) in the control of the potato cyst nematode Globodera pallida. The AMF used were Vaminoc (mixed-AMF inoculum), Glomus intraradices (BioRize BB-E) and G. mosseae (isolate BEG 12). In the absence of AMF, the in-soil hatch of G. pallida increased 30% (P < 0.01) from wk-2 to wk-4 after planting. Inoculation of physiologically-aged potato (cv. Golden Wonder) tubers with AMF eliminated this delay in G. pallida hatch by stimulating a mean increase of 32% (P < 0.01) in hatch within 2 wk after planting. In the aldicarb-treated plots in Experiment 1, G. pallida multiplication rate was 38% lower (P < 0.05) in roots of AMF-inoculated than noninoculated plants, but in Experiment 2, this effect was slightly lower (P = 0.07). In these plots, the single AMF inocula showed also a weak trend (P = 0.10) towards greater tuber yields relative to their noninoculated counterparts. Mycorrhization therefore appears to enhance the efficacy of carbamate nematicides against G. pallida and consequently more research is proposed to validate these findings and fully explore the potential of this model.