Landfills determine the distribution of an expanding breeding population of the endangered Egyptian Vulture Neophron percnopterus

Human activities provide food resources for animals that are predictable in space and/or time. These resources, sometimes referred to as predictable anthropogenic food subsidies (PAFS), can be either the result of human‐generated waste or provided intentionally, sometimes as a conservation measure. Some PAFS, including landfills, are used by common species. However, little information exists about the effects that these feeding points have on rarer species that feed there, some of which are of conservation concern. This study focuses on the influence of PAFS and their spatial location on the distribution of territories of the endangered Egyptian Vulture Neophron percnopterus. We analysed a population in the NE Iberian Peninsula that has in recent decades expanded its range. We used both null model and linear model analyses to ascertain the effect of PAFS and other covariates on the occupancy of territories by the study species. PAFS appeared to play an important role in territory selection by Egyptian Vultures, as occupied territories were nearer landfills than expected by chance. Furthermore, the distance from PAFS (landfills and vulture feeding stations, or ‘restaurants’) played an important role in the probability of territory occupancy by Egyptian Vultures, in addition to other environmental variables such as surface areas of rocky south‐facing slopes, human settlement and the proximity of conspecifics. However, recent EU legislation aims to phase out open‐air landfills to reduce the negative environmental effects of these facilities. This could have an undesired impact on the endangered species that use these feeding points. We recommend management measures that can control abundant pest species but, in the long term, other measures as supplementary feeding should be considered to counteract the probable negative effect of the disappearance of landfills on endangered species.     

Enzymatic properties of vesicle-reconstituted human cytochrome P450SCC (CYP11A1) differences in functioning of the mitochondrial electron-transfer chain using human and bovine adrenodoxin and activation by cardiolipin.

The recently reported heterologous expression and purification of both human cytochrome P450SCC and adrenodoxin [Woods, S.T., Sadleir, J., Downs, T., Triantopoulos, T., Haedlam, M.J. & Tuckey, R.C. (1998) Arch. Biochem. Biophys. 353, 109-115] has enabled us to perform studies with the membrane-reconstituted human enzymes to better understand the side-chain cleavage reaction in humans. Human P450SCC was successfully reconstituted into dioleoylphosphatidylcholine vesicles with and without cardiolipin and its enzymatic properties characterized in the membrane-bound state. Enhancement of the P450SCC activity and significant activation by cardiolipin were observed when human adrenodoxin instead of bovine adrenodoxin was used as electron donor. In the absence of cardiolipin, Km for cholesterol was decreased twice in the case of human adrenodoxin indicating enhanced cholesterol binding. On the other hand, in the presence of cardiolipin in the membrane both Km and V for cholesterol were decreased with human adrenodoxin as electron donor. Kinetic analysis of the interaction between human P450SCC and its redox partners provided evidence for enhanced binding of the human electron donor to human P450SCC indicated by both an increased V and decreased Kd for human adrenodoxin compared with the values with bovine adrenodoxin. Because no similar effects were observed in Tween 20 micelles, these results suggest that the phospholipid membrane may play an important role in the interaction of human adrenodoxin with human P450SCC.     

Genetic tagging: contemporary molecular ecology

Population genetic analyses have been highly successful in deciphering inter- and intra-specific evolutionary relationships, levels of gene flow, genetic divergence and effective population sizes. Parameters estimated by traditional population genetic analyses are evolutionary averages and thus not necessarily relevant for contemporary ecological or conservation issues. Molecular data can, however, also provide insight into contemporary patterns of divergence, population size and gene flow when a sufficient number of variable loci are analysed to focus subsequent data analyses on individuals rather than populations. Genetic tagging of individuals is an example of such individual-based approaches and recent studies have shown it to be a viable alternative to traditional tagging methods. Owing to the ubiquitous presence of hyper-variable DNA sequences in eukaryote genomes it is in principle possible to tag any eukaryote species and the required DNA can be obtained indirectly from substrates such as faeces, sloughed skin and hair. The purpose of this paper is to present the concept of genetic tagging and to further advocate the extension of individual-based genetic analyses beyond the identification of individuals to other kinds of relationships, such as parent-offspring relations, which more fully exploit the genetic nature of the data.     

Class-1 polypeptide chain release factors are structurally and functionally similar to suppressor tRNAs and comprise different structural-functional families of prokaryotic/mitochondrial and eukaryotic/archaebacterial factors

Class-1 polypeptide chain release factors (RF) induce peptidyl-tRNA hydrolysis in the ribosome if any of the three stop codons encounters the ribosomal A site. We have shown earlier that all factors of this class possess a common functionally essential motif GGQ. In this study we analyzed the primary structures of all known class-1 factors taken from the data banks together with the experimental data available on their structural and functional organization. The following conclusions were drawn. 1. Amino acid sequences of eukaryotic and archaebacterial factors (eRF1 and aRF1, respectively) show high similarity. This suggests the potential ability of eRF1 to function in archaebacterial and aRF1 in eukaryotic ribosomes, and points to their origin from a common ancestor. 2. Primary structures of class-1 release factors from prokaryotes and enkaryotic mitochondria show no statistically significant similarity with archaebacterial and cytoplasmic eukaryotic release factors, except for a common motif GGQ. This confirms our earlier conclusion (Nature, 1994, vol. 372, pp. 701–703) and contradicts the hypothesis of Itoet al. (Proc. Natl. Acad. Sci. USA, 1996, vol. 93, pp. 5443–5448) about structural similarity of all class-1 release factors. 3. All the eRF1/aRF1 recognizing three stop codons have a common motif NIKs that is absent from eubacterial RF1 and RF2, each of which is able to recognize two stop codons of the three. We suppose that the function of the NIKs motif is to fix the proper orientation of eRF1/aRF1 at the ribosome. 4. The domain structure and functional properties of eRF1/aRF1 point to the similarity of these factors with suppressor tRNAs as suggested long ago, and also semblance with aminoacyl-tRNA synthetases. 5. Considering that peptidyl-tRNA is fixed at the ribosomal P site while the stop codon and termination factor are at the A site, it may be presumed that the distance between the functionally essential motifs NIKs and GGQS in eRF1/aRF1 should approximately correspond to the distance between the anticodon and the aminoacyl end of aminoacyl-tRNA located at the ribosomal A site.     

How does <Emphasis Type="Italic">Euplotes</Emphasis> translation termination factor eRF1 fail to recognize the UGA stop codon?

Class 1 eukaryotic release factor 1 (eRF1) recognizes all three stop codons (UAA, UAG, and UGA) in standard-code organisms. In some ciliates with variant genetic codes, one or two stop codons are used to encode amino acids and are not recognized by eRF1; e.g., UAA and UAG are reassigned to Gln in Stylonychia and UGA is reassigned to Cys in Euplotes. Stop codon recognition is due to the N-terminal domain of eRF1 in standard-code organisms. Since variant-code ciliates most likely originate from universal-code ancestors, the N-domain sequence of their eRF1 was assumed to harbor the residues that are responsible for the changes in stop codon recognition specificity. To identify the N-domain regions determining the UGA-only specificity of Euplotes aediculatus eRF1, chimeric proteins were constructed by swapping various N-domain fragments of the E. aediculatus for their human counterparts; the MC domain was from human eRF1. Functional analysis of the chimeric eRF1 in vivo revealed two regions (residues 38–50 and 123–145) restricting the E. aediculatus eRF1 specificity to UAR. The change in stop codon recognition specificity of eRF1 was regarded as the first step in the origin of the variant genetic code in ciliates.