Identification of a novel polyproline recognition site in the cytoskeletal associated protein, proline serine threonine phosphatase interacting protein.
Abstract
Protein-protein interactions are often mediated by the recognition of proline-rich domains by SH3 or WW modules. Previously, we demonstrated that the PEST-type protein-tyrosine phosphatase, PTP HSCF (hematopoietic stem cell fraction), bound to a novel cytoskeletal associated protein, proline serine threonine phosphatase interacting protein (PST PIP), via an interaction between the proline-rich COOH terminus of the PTP and a site within the putative coiled-coil domain of PST PIP. Here we describe a more detailed analysis of this interaction. Earlier data suggested that the NH2 terminus of PST PIP was important for binding to the phosphatase, and deletion of the NH2-terminal 50 amino acids of the PST PIP resulted in an apparently misfolded protein that was incapable of binding PTP HSCF. To examine the region involved with binding to PTP HSCF, alanine-scanning mutants were produced at intervals throughout PST PIP. This analysis demonstrated that a tryptophan at position 232 was essential for binding in vitro. Transfection experiments demonstrated that the Trp232 mutant protein was capable of association with the cortical cytoskeleton but was not bound to PTP HSCF in vivo. Alanine scanning of a peptide derived from the COOH-termina...Continue Reading
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