Phostensin, a protein phosphatase 1 F-actin cytoskeleton targeting subunit encoded by KIAA1949, consists of 165 amino acids and is located between HLA-C and HLA-E gene clusters on human chromosome 6. In this current study, we characterized the biochemical functions of phostensin. Actin dynamics assays using gelsolin-actin seeds showed that phostensin decreases the elongation and depolymerization rates of actin. lament pointed ends. The feature of phostensin that binds to the pointed ends of actin. laments was observed through fluorescent single. lament binding assay. Taken together, our results suggested that phostensin is an actin. lament pointed end-capping protein that is capable of modulating actin dynamics. (C) 2009 Elsevier Inc. All rights reserved.