Widespread Occurrence of Black-Orange-Black Color Pattern in Hymenoptera.

Certain color patterns in insects show convergent evolution reflecting potentially important biological functions, for example, aposematism and mimicry. This phenomenon has been most frequently documented in Lepidoptera and Coleoptera, but has been less well investigated in Hymenoptera. It has long been recognized that many hymenopterans, especially scelionids (Platygastridae), show a recurring pattern of black head, orange/red mesosoma, and black metasoma (BOB coloration). However, the taxonomic distribution of this striking color pattern has never been documented across the entire order. The main objective of our research was to provide a preliminary tabulation of this color pattern in Hymenoptera, through examination of museum specimens and relevant literature. We included 11 variations of the typical BOB color pattern but did not include all possible variations. These color patterns were found in species belonging to 23 families of Hymenoptera, and was most frequently observed in scelionids, evaniids, and mutillids, but was relatively infrequent in Cynipoids, Diaprioids, Chalcidoids, and Apoids. The widespread occurrence of this color pattern in Hymenoptera strongly suggests convergent evolution and a potentially important function. The BOB color pattern was found in species from all biogeographic regions and within a species it was usually present in both sexes (with a few notable exceptions). In better studied tropical regions, such as Costa Rica, this color pattern was more common in species occurring at lower elevations (below 2,000 m). The biology of the tabulated taxa encompasses both ecto- and endoparasitoids, idiobionts and koinobionts, from a diversity of hosts, as well as phytophagous sawflies.

Artificial chaperone-assisted refolding of citrate synthase.

The power of genetic engineering methods, along with increasing genomic information, makes heterologous expression of proteins an extremely important biochemical tool. Unfortunately, proteins obtained in this way often are not in their native form, and folding becomes a crucial step in protein production. We have recently developed a strategy that promotes the folding of chemically denatured proteins via the sequential addition of low molecular weight "artificial chaperones." Here we describe in detail the application of this method to porcine heart citrate synthase. Refolding yields of as high as 65% have been achieved. Mechanistic studies indicate that there are significant differences between artificial chaperone-assisted refolding of citrate synthase and artificial chaperone-assisted refolding of two other proteins that have been examined, carbonic anhydrase B (Rozema, D., and Gellman, S. H. (1996) J. Biol. Chem. 271, 3478-3487) and lysozyme (Rozema, D., and Gellman, S. H. (1996) Biochemistry 35, 15760-15771). The differences among these three test proteins reveal the range of procedural variation that must be considered in the application of the artificial chaperone method to new proteins.

Mechanistic comparison of artificial-chaperone-assisted and unassisted refolding of urea-denatured carbonic anhydrase B.

BACKGROUND: We have previously described a method for the refolding of chemically denatured proteins in which small molecules ('artificial chaperones', a detergent and cyclodextrin) assist renaturation. In a previous analysis of lysozyme refolding from the GdmCl-denatured, DTT-reduced state, we found that enzymatic activity is regained at indistinguishable rates for unassisted (absence of additives) and artificial-chaperone-assisted refolding. While unassisted and artificial-chaperone-assisted refolding rates could also be directly compared for GdmCl-denatured bovine carbonic anhydrase B (CAB), only cationic detergents could be used as assistants. We therefore set out to determine whether artificial chaperones could assist the refolding of urea-denatured CAB, whether the charge and structure of the detergent used affects refolding assistance, and, if so, whether the assistance is mechanistically similar to that observed for GdmCl-denatured CAB. RESULTS: Our results indicate that CAB can be refolded from the urea-denatured state via the artificial chaperone process, using both anionic and cationic detergents. There is a distinctive product-determining step early in the artificial-chaperone-assisted refolding mechanism, but the rate-determining steps of the unassisted and artificial-chaperone-assisted processes are indistinguishable. CONCLUSIONS: Because the rate-determining steps of unassisted and artificial-chaperone-assisted refolding are indistinguishable, we conclude that the rate-determining step of CAB refolding is unaffected by the use of artificial chaperones. Our observations also suggest that denatured CAB undergoes a slow partial folding in concentrated urea solution.