O-LINKED L-FUCOSE IS PRESENT IN DESMODUS-ROTUNDUS SALIVARY PLASMINOGEN-ACTIVATOR

DSPA alpha 1 (Desmodus rotundus salivary plasminogen activator), a pla sminogen activator from the saliva of the vampire bat Desmodus rotundu s, is an effective thrombolytic agent. An unusual type of posttranslat ional modification, in which L-fucose is O-glycosidically linked to th reonine 61 in the epidermal growth factor domain was found for natural DSPA alpha 1 and its recombinant form isolated from Chinese hamster o vary cells. In the present study a combination of carbohydrate and ami no acid composition analysis, amino acid sequencing, and mass spectrom etry revealed that the L-fucose is bound to residues 56-68 of DSPA alp ha 1. The amino acid sequence of this glycosylation site agreed with t he suggested consensus sequence Cys-Xaa-Xaa-Gly-Gly-Ser/Thr-Cys descri bed for other proteins, A new strategy for the identification of the m odified amino acid was established. Direct evidence for the occurrence of fucosyl-threonine was obtained by mass spectrometry after digestio n of the glycopeptide with a mixture of peptidases. On the basis of th ese results, DSPA alpha 1 is a suitable model for studying the influen ce of O-fucosylation on clearance rates, particularly in comparative s tudies with the identically fucosylated and structurally related tissu e plasminogen activator.