Incorporating stakeholder preferences in the selection of technologies for using invasive alien plants as a bio-energy feedstock: applying the analytical hierarchy process.

Invasive alien plants (IAPs) impose significant social costs on the population of the Agulhas Plain region in South Africa due to their adverse impacts on ecosystem goods and services (decreased water supply and increased fire risk). While the cost of clearing IAPs is considerable, this paper assesses opportunities to reduce some of the social and environmental burdens (e.g. disruptions of ecosystems which have negative impacts on livelihoods) by using IAP biomass to produce bio-energy. However, such an initiative could increase financial dependency on these plants and is thus considered to be a major risk factor which could create adverse incentives to illegally grow these plants. A participatory decision-making process with active stakeholder participation is a key element in managing such an initiative. We used a multi-stakeholder engagement process and the analytical hierarchy process to define and weigh suitable criteria for the assessment of different "IAP biomass to bio-energy" technology scenarios on the Agulhas Plain. Feasible scenarios were constructed by means of an expert panel which were then ranked according to stakeholder preference. The six criteria were: minimising impacts on natural resources; job creation; certainty of benefits to local people in the study area; development of skills for life; technology performance and cost efficiency. This ranking was largely determined by the preference for resource efficiency in terms of minimising impacts on natural ecosystems and the localisation of benefits. The smaller, modular technologies were consequently preferred since these realise direct local benefits while developing local skills and capacity in their manufacture, sales and maintenance. The rankings as obtained in this study are context-bound, which implies that the findings only have limited application to areas with similar biophysical and socio-economic characteristics. However, the method itself is fully generalisable, and the same prioritisation process can be followed in any study area to ensure that a participatory decision-making process fulfils local energy needs and contributes to sustainable development.

The merozoite surface protein 6 gene codes for a 36 kDa protein associated with the Plasmodium falciparum merozoite surface protein-1 complex.

A complex of non-covalently bound polypeptides is located on the surface of the merozoite form of the human malaria parasite Plasmodium falciparum. Four of these polypeptides are derived by proteolytic processing of the merozoite surface protein 1 (MSP-1) precursor. Two components, a 22 and a 36 kDa polypeptide are not derived from MSP-1. The N-terminal sequence of the 36 kDa polypeptide has been determined, the corresponding gene cloned, and the protein characterised. The 36 kDa protein consists of 211 amino acids and is derived from a larger precursor of 371 amino acids. The precursor merozoite surface protein 6 (MSP-6) has been designated, and the 36 kDa protein, MSP-6(36). Mass spectrometric analysis of peptides released from the polypeptide by tryptic digestion confirmed that the gene identified codes for MSP-6(36). Antibodies were produced to a recombinant protein containing the C-terminal 45 amino acid residues of MSP-6(36). In immunofluorescence studies these antibodies bound to antigen at the parasite surface or in the parasitophorous vacuole within schizonts, with a pattern indistinguishable from that of antibodies to MSP-1. MSP-6(36) was present in the MSP-1 complex immunoprecipitated from the supernatant of in vitro parasite cultures, but was also immunoprecipitated from this supernatant in a form not bound to MSP-1. Examination of the MSP-6 gene in three parasite lines detected no sequence variation. The sequence of MSP-6(36) is related to that of the previously described merozoite surface protein 3 (MSP-3). The MSP-6(36) amino acid sequence has 50% identity and 85% similarity with the C-terminal region of MSP-3. The proteins share a specific sequence pattern (ILGWEFGGG-[AV]-P) and a glutamic acid-rich region. The remainder of MSP-6 and MSP-3 are unrelated, except at the N-terminus. Both MSP-6(36) and MSP-3 are partially associated with the parasite surface and partially released as soluble proteins on merozoite release. MSP-6(36) is a hydrophilic negatively charged polypeptide, but there are two clusters of hydrophobic amino acids at the C-terminus, located in two amphipathic helical structures identified from secondary structure predictions. It was suggested that this 35 residue C-terminal region may be involved in MSP-6(36) binding to MSP-1 or other molecules; alternatively, based on the secondary structure and coil formation predictions, the region may form an intramolecular anti-parallel coiled-coil structure.

A subtilisin-like protein in secretory organelles of Plasmodium falciparum merozoites.

In the vertebrate host, the malaria parasite invades and replicates asexually within circulating erythrocytes. Parasite proteolytic enzymes play an essential but poorly understood role in erythrocyte invasion. We have identified a Plasmodium falciparum gene, denoted pfsub-1, encoding a member of the subtilisin-like serine protease family (subtilases). The pfsub-1 gene is expressed in asexual blood stages of P. falciparum, and the primary gene product (PfSUB-1) undergoes post-translational processing during secretory transport in a manner consistent with its being converted to a mature, enzymatically active form, as documented for other subtilases. In the invasive merozoite, the putative mature protease (p47) is concentrated in dense granules, which are secretory organelles located toward the apical end of the merozoite. At some point following merozoite release and completion of erythrocyte invasion, p47 is secreted from the parasite in a truncated, soluble form. The subcellular location and timing of secretion of p47 suggest that it is likely to play a role in erythrocyte invasion. PfSUB-1 is a new potential target for antimalarial drug development.

Isolation, expression and characterization of the gene for an ADP-ribosylation factor from the human malaria parasite, Plasmodium falciparum.

We have isolated an ADP-ribosylation factor (ARF) gene from the human malarial parasite, Plasmodium falciparum. The gene (P. falciparum arf1) has four introns and the exons encode a protein of 181 amino acids with high similarity to the mammalian class I ARF proteins 1-3 (> or = 74% amino acid identity). Southern hybridization suggests there is at least one additional arf in the P. falciparum genome. Northern analysis identified a single P. falciparum arf1 mRNA of 1.8 kb in the asexual blood stage form of the parasite. The P. falciparum arf1 mRNA levels are developmentally regulated, reaching a maximum during nuclear division towards the end of the intraerythrocytic cycle. P. falciparum arf1 cDNA was isolated by reverse-transcriptase polymerase chain reaction and used to express a recombinant protein in Escherichia coli. Recombinant P. falciparum ARF1 protein was purified with stoichiometric amounts of bound GDP, although intrinsic guanose triphosphatase activity of the protein could not be detected. The protein stimulated cholera-toxin-catalyzed ADP-ribosyltransferase activity in a reaction that was dependent upon the addition of both dimyristoylglycerophosphocholine and cholate. The protein bound GTP with first-order kinetics with an apparent rate constant, k', of 0.0145 (+/- 0.0019) min-1. These results suggest that P. falciparum ARF1 is a member of the class 1 ARF family and provide additional evidence for the existence of a classical secretory pathway in P. falciparum.

A 22 kDa protein associated with the Plasmodium falciparum merozoite surface protein-1 complex.

The Plasmodium falciparum merozoite surface protein-1 (MSP-1) is synthesized as a precursor of approximately 195 kDa and is processed to form a complex of polypeptides on the surface of free merozoites. As a result of a second processing event, the entire MSP-1 complex is shed from the surface, apart from a C-terminal fragment that remains anchored to the merozoite membrane. We have identified a 22 kDa protein (p22) on the surface of merozoites by cell surface radioiodination and indirect immunofluorescence assay on unfixed free merozoites. p22 is also a component of the shed MSP-1 complex where it is present in part as a 19 kDa form (p22(19)) as shown by immunochemical and peptide mapping analyses. The soluble complex contains MSP-1-derived polypeptides and p22 in approximately stoichiometrically equal amounts. N-terminal amino acid sequence analyses of p22/p22(19) showed that the protein is not derived from the MSP-1 precursor.