Meeting Abstract
Embryos of the brine shrimp, Artemia franciscana, employ a set of highly hydrophilic polypeptides, termed LEA proteins, to survive severe desiccation. Most LEA proteins belong to a larger group of intrinsically disordered proteins (IDPs), which have little or no well-defined secondary structure at physiological water concentrations. However, LEA proteins become more ordered at low water concentrations during desiccation. Unlike other anhydrobiotic animals which only express group 3 LEA proteins, A. franciscana expresses proteins from multiple groups; groups 1 (AfrLEA1.3), 3 (AfrLEAI, AfrLEA2, AfrLEA3m), and 6 (AfrSMP). By employing a number of bioinformatics approaches, we assess potential folding patterns at low intracellular water concentrations as well as potential functions based on predicted secondary structures. According to MeDOR analysis, group 1 LEA proteins, do not appear to become very ordered, even at low water concentrations. In contrast, group 3 LEA proteins exhibit about 50 – 60% of ordered regions, often forming alpha helices. Using Heliquest and DeepView, we predict that some of these alpha helices are amphipathic, which implies a potential for membrane interactions. Additionally, AfrLEAI has a unique spacing of proline residues (~44-40 aa apart) surrounded by hydrophobic residues that separate the predicted helices. Furthermore, GlobPlot analysis suggests three regions of coiled-coil structure in AfrLEAI. PONDR analysis suggests that AfrSMP is an atypical LEA protein, which becomes more disordered as the cell desiccates. Transgenic expression and purification of AfrLEAI, AfrLEA1.3, and AfrSMP are currently underway, and experiments to support these predictions will be performed when isolated proteins become available. Supported by NSF IOS-1457061/IOS-1456809.
