title: Dictyostelium myosin-IE is a fast molecular motor involved in phagocytosis.
abstract: Class I myosins are single-headed motor proteins, implicated in various motile processes including organelle translocation, ion-channel gating, and cytoskeleton reorganization. Here we describe the cellular localization of myosin-IE and its role in the phagocytic uptake of solid particles and cells. A complete analysis of the kinetic and motor properties of Dictyostelium discoideum myosin-IE was achieved by the use of motor domain constructs with artificial lever arms. Class I myosins belonging to subclass IC like myosin-IE are thought to be tuned for tension maintenance or stress sensing. In contrast to this prediction, our results show myosin-IE to be a fast motor. Myosin-IE motor activity is regulated by myosin heavy chain phosphorylation, which increases the coupling efficiency between the actin and nucleotide binding sites tenfold and the motile activity more than fivefold. Changes in the level of free Mg(2+) ions, which are within the physiological range, are shown to modulate the motor activity of myosin-IE by inhibiting the release of adenosine diphosphate.
authors.affiliation: Abteilung Biophysik, Max-Planck Institut für medizinische Forschung, Jahnstr. 29, 69120 Heidelberg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Dürrwang
authors.forename: Setsuko
authors.initials: S
authors.lastname: Fujita-Becker
authors.forename: Muriel
authors.initials: M
authors.lastname: Erent
authors.forename: F Jon
authors.initials: FJ
authors.lastname: Kull
authors.forename: Georgios
authors.initials: G
authors.lastname: Tsiavaliaris
authors.forename: Michael A
authors.initials: MA
authors.lastname: Geeves
authors.forename: Dietmar J
authors.initials: DJ
authors.lastname: Manstein
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D024461:Myosin Type I / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis / Q000502:physiology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000502:physiology
chemical_list: D000244:Adenosine Diphosphate; D024461:Myosin Type I; D008274:Magnesium