Non-conservation Area Research Articles

Botulinum Neurotoxin G Binds Synaptotagmin-II in a Mode Similar to That of Serotype B: Tyrosine 1186 and Lysine 1191 Cause Its Lower Affinity

Botulinum neurotoxins (BoNTs) block neurotransmitter release by proteolyzing SNARE proteins in peripheral nerve terminals. Entry into neurons occurs subsequent to interaction with gangliosides and a synaptic vesicle protein. Isoforms I and II of synaptotagmin were shown to act as protein receptors for two of the seven BoNT serotypes, BoNT/B and BoNT/G, and for mosaic-type BoNT/DC. BoNT/B and BoNT/G exhibit a homologous binding site for synaptotagmin whose interacting part adopts helical structure upon binding to BoNT/B. Whereas the BoNT/B-synaptotagmin-II interaction has been elucidated in molecular detail, corresponding information about BoNT/G is lacking. Here we systematically mutated the synaptotagmin binding site in BoNT/G and performed a comparative binding analysis with mutants of the cell binding subunit of BoNT/B. The results suggest that synaptotagmin takes the same overall orientation in BoNT/B and BoNT/G governed by the strictly conserved central parts of the toxins' binding site. The surrounding nonconserved areas differently contribute to receptor binding. Reciprocal mutations Y1186W and L1191Y increased the level of binding of BoNT/G approximately to the level of BoNT/B affinity, suggesting a similar synaptotagmin-bound state. The effects of the mutations were confirmed by studying the activity of correspondingly mutated full-length BoNTs. On the basis of these data, molecular modeling experiments were employed to reveal an atomistic model of BoNT/G-synaptotagmin recognition. These data suggest a reduced length and/or a bend in the C-terminal part of the synaptotagmin helix that forms upon contact with BoNT/G as compared with BoNT/B and are in agreement with the data of the mutational analyses.

Striking a Balance: Socioeconomic Development and Conservation in Grassland through Community-Based Zoning

The goal of preserving nature is often in conflict with economic development and the aspirations of the rural poor. Nowhere is this more striking than in native grasslands, which have been extensively converted until a mere fraction of their original extent remains. This is not surprising; grasslands flourish in places coveted by humans, primed for agriculture, plantations, and settlements that nearly always trump conservation efforts. The Umgano grassland conservation and poverty reduction project in KwaZulu-Natal Province, South Africa uses community-based spatial planning to balance the conversion of its lower-conservation value grasslands to a timber plantation, while conserving higher-value grasslands for heritage purposes and managed livestock grazing. Ten years after project launch, we measured the ecological and socioeconomic impacts of the project using Normalized Differential Vegetation Index remote sensing data and over 500 household interviews, as compared with similar non-conserved areas. Zoned management of the Umgano area had resulted in between 9% and 17% greater average peak production in the grassland areas compared to control sites. There was also a 21% gain in incomes for the roughly one hundred people employed by the forestry efforts, when compared to others in their village. Community-based spatial zoning is an overlooked tool for balancing conservation and development but may require, as we found in Umgano, certain critical factors including strong local leadership, an accountable financial management mechanism to distribute income, outside technical expertise for the zoning design, and community support.

Suitability for conservation as a criterion in regional conservation network selection

The process of selecting candidate areas for inclusion in a regional conservation network should include not only delineating appropriate land units for selection and defining targets for representing features of interest, but also determining the suitability of land units for conservation purposes. We developed an explicit rating of conservation suitability by applying fuzzy-logic functions in a knowledge base to ecological condition and socio-economic attributes of land units in the interior Columbia River basin, USA. Suitability was converted to unsuitability to comprise a cost criterion in selecting regional conservation networks. When unsuitability was the sole cost criterion or was combined with land area as cost, only about one-third of the area selected was rated suitable, due to inclusion of unsuitable land to achieve representation of conservation targets (vegetation cover-type area). Selecting only from land units rated suitable produced networks that were 100% suitable, reasonably efficient, and most likely to be viable and defensible, as represented in our knowledge-based system. However, several conservation targets were not represented in these networks. The tradeoff between suitability and effectiveness in representing targets suggests that a multi-stage process should be implemented to address both attributes of candidate conservation networks. The suitability of existing conservation areas was greater than that of most alternative candidate networks, but 59% of land units containing conservation areas received a rating of unsuitable, due in part to the presence of units only partially occupied by conservation areas, in which unsuitability derived from conditions in non-conserved areas.

Anthropogenic influences on potential fire spread in a pyrogenic ecosystem of Florida, USA

Fire has historically been an important ecological factor maintaining southeastern U.S. vegetation. Humans have altered natural fire regimes by fragmenting fuels, introducing exotic species, and suppressing fires. Little is known about how these alterations specifically affect spatial fire extent and pattern. We applied historic (1920 and 1943) and current (1990) GIS fuels maps and the FARSITE fire spread model to quantify the differences between historic and current fire spread distributions. We held all fire modeling variables (wind speed and direction, cloud cover, precipitation, humidity, air temperature, fuel moistures, ignition source and location) constant with exception of the fuel models representing different time periods. Model simulations suggest that fires during the early 1900's burned freely across the landscape, while current fires are much smaller, restricted by anthropogenic influences. Fire extent declined linearly with patch density, and there was a quadratic relationship between fire extent and percent landscape covered by anthropogenic features. We found that as little as 10 percent anthropogenic landcover caused a 50 percent decline in fire extent. Most landscapes (conservation or non-conservation areas) are now influenced by anthropogenic features which disrupt spatial fire behavior disproportionately to their actual size. These results suggest that land managers using fire to restore or maintain natural ecosystem function in pyrogenic systems will have to compensate for anthropogenic influences in their burn planning.

Bovine T cells specific for Trypanosoma brucei brucei variant surface glycoprotein recognize nonconserved areas of the molecule.

The specificity of bovine CD4+ T-cell responses to Trypanosoma brucei variant surface glycoprotein (VSG) has been examined by using a panel of seven T-cell clones and nested deletions of the ILTat 1.3 VSG gene expressed in Escherichia coli. All clones recognized the polymorphic N-terminal domain of the antigen, and the recognition sites of five of the clones were resolved to three areas with lengths of 14, 18, and 21 amino acids. Comparison of these regions with corresponding areas of other VSG molecules, including those derived from the same trypanosomal serodeme, has shown that the sites are not conserved. In the light of recent observations that VSG-specific T-cell responses are induced in mice infected with T. brucei, these results confirm with the belief that immune pressure from T cells may contribute to the generation of antigenic diversity on the surface of African trypanosomes.

Reassortment of DNA recognition domains and the evolution of new specificities.

Type I restriction enzymes comprise three subunits only one of which, the S polypeptide, dictates the specificity of the DNA sequence recognized. Recombination between two different hsdS genes, SP and SB, led to the isolation of a system, SQ, which had a different specificity from that of either parent. The finding that the nucleotide sequence recognized by SQ is a hybrid containing components from both the SP and SB target sequences suggested that DNA recognition is carried out by two separable domains within each specificity polypeptide. To test this we have made the recombinant gene of reciprocal structure and demonstrate that it encodes a polypeptide whose recognition sequence, deduced in vivo, is as predicted by this model. We also report the sequence of the SB specificity gene, so that information is now available for the five known members of this family of enzymes. All show a similar organization of conserved and variable regions. Comparisons of the predicted amino acid sequences reveal large non-conserved areas which may not even be structurally similar. This is remarkable since these different S subunits are functionally identical, except for the specificity with respect to the DNA sequence with which they interact. We discuss the correlation of the variation in polypeptide sequence with recognition specificities.