The cytoskeletal protein talin is O-glycosylated

Talin is a 215-kDa cytoskeletal protein implicated in linking actin filaments to the plasma membrane. We show here that chicken gizzard talin is galactosylated by incubation with UDP-[3H]galactose and galactosyl-transferase. The labeled carbohydrate moiety is removed by beta-elimination and comigrates with Gal beta 1-4GlcNAcitol, indicating that talin belongs to a recently discovered class of cytosolic proteins carrying N-acetylglucosamine (GlcNAc) O-linked to serine or threonine (Holt, G. D., and Hart, G. W. (1986) J. Biol. Chem. 261, 8049-8057). Two glycosylated sequences were identified in the tail domain of talin: ANQAIQMAXQNLVDPAXTQ and GILANQLTNDYGQLAQQ, corresponding to amino acids 1470-1488 and 1883-1899, respectively, of the mouse talin amino acid sequence (Rees, D. J. G., Ades, S. E., Singer, S. J., and Hynes, R. O. (1990) Nature 347, 685-689). The putative glycosylation sites are PAXTQ and QLTND. At most 6% of chicken gizzard talin and 3% of porcine stomach talin are galactosylated by galactosyltransferase. Furthermore, human platelet talin is not labeled at all by the procedure, indicating that it may not be glycosylated.