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Flagellar glycoprotein synthesis and mobilization of flagellar glycoprotein pools have been followed during flagellar regeneration in Euglena . The glycosylation inhibitor tunicamycin has little effect on either regeneration kinetics or the complement of flagellar peptides as seen in SDS acrylamide gels, but tunicamycin totally inhibits incorporation of exogenously supplied [ t4 C]xylose into flagellar glycoproteins . Moreover, deflagellated cells pulsed with tunicamycin for 30 min or more, regenerated for 180 min, and then redeflagellated are completely or partially inhibited from undergoing a second regeneration even when tunicamycin is no longer present. These facts are interpreted as indicating that Euglena retains sufficient glycoprotein pool for one complete flagellar assembly . Some of this pool is present on the cell surface since [' 25 1]-labeled surface peptides can be chased into the regenerating flagellum . Glycosylation may also be taking place in the flagellum directly because [ 14 C] xylose has been found in three flagellar fractions: glycoprotein and two others, which are lipophilic and have properties similar to those described for lipid-carrier glycoprotein intermediates in other systems. Pulse-chase experiments also suggest a precursor-product relationship between the presumptive lipid carriers and flagellar glycoproteins . From these results a model is postulated in which Euglena is visualized as retaining sufficient pool of glycoprotein for one complete flagellar regeneration, but the pool is normally supplemented by active xylosylation in situ during regeneration .During regeneration the flagellar membrane and its associated surface glycoproteins such as mastigonemes and scales are assembled in a relatively short period after flagellar withdrawal or excision . As with the well-studied flagellar axonemes, the regenerating flagellum can also be used to identify precursors and the mobilization of the components of the flagellar surface, and to determine how much, if any, control they exert on regeneration . In Euglena such analyses are facilitated by the distinctive properties of the flagellar surface when compared with those of the remainder of the cell . The predominance of xylose as the major saccharide of the abundant flagellar glycoproteins is particularly striking since other regions of the cell have no detectable quantities of this sugar (8). This unique biochemical marker suggested that flagellar glycoproteins might be selectively identified and their assembly and insertion followed in appropriate regeneration experiments . Evidence is presented in this report that exogenously added [t'CJxylose is incorporated into flagellar glycolipids and glycoproteins. This has permitted the tentative identification of putative lipid intermediates in the flagellum, of substantial glycoprotein 432 M.

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