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Actinomycetales are known to produce various secondary metabolites including products with surface-active and emulsifying properties known as biosurfactants. In this study, the nonpathogenic actinomycetes Tsukamurella spumae and Tsukamurella pseudospumae are described as producers of extracellular trehalose lipid biosurfactants when grown on sunflower oil or its main component glyceryltrioleate. Crude extracts of the trehalose lipids were purified using silica gel chromatography. The structure of the two trehalose lipid components (TL A and TL B) was elucidated using a combination of matrix-assisted laser desorption/ionization time-of-flight/time-of-flight/tandem mass spectroscopy (MALDI-ToF-ToF/MS/MS) and multidimensional NMR experiments. The biosurfactants were identified as 1-α-glucopyranosyl-1-α-glucopyranosid carrying two acyl chains varying of C4 to C6 and C16 to C18 at the 2' and 3' carbon atom of one sugar unit. The trehalose lipids produced demonstrate surface-active behavior and emulsifying capacity. Classified as risk group 1 organisms, T. spumae and T. pseudospumae hold potential for the production of environmentally friendly surfactants.

Activation of phototransduction in the compound eye of Drosophila is mediated by a heterotrimeric G protein that couples to the effector enzyme phospholipase C␤. The ␥ subunit of this G protein (G␥e) as well as ␥ subunits of vertebrate transducins contain a carboxyl-terminal CAAX motif (C, cysteine; A, aliphatic amino acid; X, any amino acid) with a consensus sequence for protein farnesylation. To examine the function of G␥e farnesylation, we mutated the farnesylation site and overexpressed the mutated G␥e in Drosophila. Mass spectrometry of overexpressed G␥e subunits revealed that nonmutated G␥e is modified by farnesylation, whereas the mutated G␥e is not farnesylated. In the transgenic flies, mutated G␥e forms a dimeric complex with G␤e, with the consequence that the fraction of non-membrane-bound G␤␥ is increased. Thus, farnesylation of G␥e facilitates the membrane attachment of the G␤␥ complex. We also expressed human G␥rod in Drosophila photoreceptors. Despite similarities in the primary structure between the transducin ␥ subunit and Drosophila G␥e, we observed no interaction of human G␥rod with Drosophila G␤e. This finding indicates that human G␥rod and Drosophila G␥e provide different interfaces for the interaction with G␤ subunits. Electroretinogram recordings revealed a significant loss of light sensitivity in eyes of transgenic flies that express mutated G␥e. This loss in light sensitivity reveals that post-translational farnesylation is a critical step for the formation of membrane-associated G␣␤␥ required for transmitting light activation from rhodopsin to phospholipase C␤.