Current methods for phospholipid synthesis involving acylation of sn-glycero-3-phosphorylcholine, lysolecithins, and related glycerophosphate esters are not satisfactory. With NN-dimethyl4aminopyridine as a catalyst and moderate amounts of fatty acid anhydrides (1.2-1.5 mol equiv per OH group), diacyl or 1,2-mixed diacylphosphatidyicholines, Nprotected phosphatidylethanolamines, and phosphatidic acids now can be conveniently prepared in high yields (75-90%). New phospholipids containing photoactivable groups, such as trifluorodiazopropionyl, diazirinophenoxy, 2-nitro-4-azidophenoxy, m-azidophenoxy, and a,3-unsaturated keto groups, in the fatty acyl chains have been prepared. These phospholipids are of interest in studies of lipid-lipid and lipid-protein interactions in biological membranes.

SummaryADF/cofilins are ubiquitous actin dynamics-regulating proteins that have been mainly implicated in actinbased cell motility. Trypanosomatids, e.g. Leishmania and Trypanosoma, which mediate their motility through flagellum, also contain a putative ADF/cofilin homologue, but its role in flagellar motility remains largely unexplored. We have investigated the role of this protein in assembly and motility of the Leishmania flagellum after knocking out the ADF/cofilin gene by targeted gene replacement. The resultant mutants were completely immotile, short and stumpy, and had reduced flagellar length and severely impaired beat. In addition, the assembly of the paraflagellar rod was lost, vesicle-like structures were seen throughout the length of the flagellum and the state and distribution of actin were altered. However, episomal complementation of the gene restored normal morphology and flagellar function. These results for the first time indicate that the actin dynamics-regulating protein ADF/ cofilin plays a critical role in assembly and motility of the eukaryotic flagellum.

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SummaryActin-based myosin motors have a pivotal role in intracellular trafficking in eukaryotic cells. The parasitic protozoan organism Leishmania expresses a novel class of myosin, myosin XXI (Myo21), which is preferentially localized at the proximal region of the flagellum. However, its function in this organism remains largely unknown. Here, we show that Myo21 interacts with actin, and its expression is dependent of the growth stage. We further reveal that depletion of Myo21 levels results in impairment of the flagellar assembly and intracellular trafficking. These defects are, however, reversed by episomal complementation. Additionally, it is shown that deletion of the Myo21 gene leads to generation of ploidy, suggesting an essential role of Myo21 in survival of Leishmania cells. Together, these results indicate that actin-dependent trafficking activity of Myo21 is essentially required during assembly of the Leishmania flagellum.

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