THE N-TERMINAL DOMAINS OF TENSIN AND AUXILIN ARE PHOSPHATASE HOMOLOGS

Tensin, an actin filament capping protein, and auxilin, a component of receptor-mediated endocytosis, are known to have 350 residue regions of significant sequence similarity near their N-termini (Schroder et a l., 1995, Eur J Biochem 228:297-304). Here we demonstrate that these r egions are homologous, not only to each other, but also to the catalyt ic domain of a putative protein tyrosine phosphatase (PTP) from Saccha romyces cerevisiae and to other PTPs. We propose that the PTP-like por tion of the homology region of tensin and auxilin represents a distinc t domain. A detailed sequence comparison indicates that the PTP-like d omain in tensin is unlikely to exhibit phosphatase activity, whereas i n auxilin it may possess a different phosphatase specificity from tyro sine phosphatases. It is probable that the PTP-like domains in tensin and auxilin mediate binding interactions with phosphorylated polypepti des; they may therefore represent members of a distinct class of phosp hopeptide recognition domain.