The lipid composition and expression of lipogenic enzymes in Euglena gracilis vary depending on the presence or absence of light, a feature that raises many questions with regard to development and regulation. Euglena is unique in having 2 de novo fatty acid synthetases (FASs). In addition to a true multienzyme complex aggregated FAS in the cytosol, there is a nonaggregated FAS located in the pure chloroplasts. The activity of the nonaggregated FAS seems to be dependent upon transient but crucial interactions among the enzymes and acyl carrier protein (ACP). Calcium ion and/or ACP acylation state may influence the capacities of the proteins to interact. In limited respects, the system of ACP-enzymes interaction may resemble the calmodulin-interactive proteins situation. The nature and regulation of the interactions among the proteins of the nonaggregated FAS will be proved with observations made on both intact pure chloroplasts or purified proteins. The following methods will be used to observe interactions between or among proteins: chemical cross-linking and electroimmunoblot analysis; chemical cross- linking and limited cleavage of cross-linked proteins; low angle laser light scattering spectrometry; and fluorescence and UV spectroscopy. Fatty acids are imporant building blocks of cell membranes and are fuel for living cells. This project seeks to determine how the several enzymes involved are regulated.*** //
