title: ATP-independent contractile proteins from plants.
abstract: Emerging technologies are creating increasing interest in smart materials that may serve as actuators in micro- and nanodevices. Mechanically active polymers currently studied include a variety of materials. ATP-driven motor proteins, the actuators of living cells, possess promising characteristics, but their dependence on strictly defined chemical environments can be disadvantagous. Natural proteins that deform reversibly by entropic mechanisms might serve as models for artificial contractile polypeptides with useful functionality, but they are rare. Protein bodies from sieve elements of higher plants provide a novel example. sieve elements form microfluidics systems for pressure-driven transport of photo-assimilates throughout the plant. Unique protein bodies in the sieve elements of legumes act as cellular stopcocks, by undergoing a Ca2+-dependent conformational switch in which they plug the sieve element. In living cells, this reaction is probably controlled by Ca2+-transporters in the cell membrane. Here we report the rapid, reversible, anisotropic and ATP-independent contractility in these protein bodies in vitro. Considering the unique biological function of the legume 'crystalloid' protein bodies and their contractile properties, we suggest to give them the distinctive name forisome ('gate-body'; from the Latin foris, the wing of a gate).
authors.affiliation: Institut für Allgemeine Botanik der Justus Liebig-Universität, Senckenbergstr. 17-21, D-35390 Giessen, Germany. michael.knoblauch@bio.bot1.uni-giessen.de
authors.forename: Michael
authors.initials: M
authors.lastname: Knoblauch
authors.forename: Gundula A
authors.initials: GA
authors.lastname: Noll
authors.forename: Torsten
authors.initials: T
authors.lastname: Müller
authors.forename: Dirk
authors.initials: D
authors.lastname: Prüfer
authors.forename: Ingrid
authors.initials: I
authors.lastname: Schneider-Hüther
authors.forename: Dörte
authors.initials: D
authors.lastname: Scharner
authors.forename: Aart J E
authors.initials: AJ
authors.lastname: Van Bel
authors.forename: Winfried S
authors.initials: WS
authors.lastname: Peters
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D040761:Biomimetic Materials / Q000737:chemistry; D032701:Biomimetics / Q000379:methods; D004548:Elasticity; D004574:Electromagnetic Fields; D008422:Materials Testing / Q000379:methods; D020409:Molecular Motor Proteins / Q000737:chemistry*; D009038:Motion; D036103:Nanotechnology / Q000379:methods*; D010940:Plant Proteins / Q000737:chemistry* / Q000528:radiation effects*; D011487:Protein Conformation; D013314:Stress, Mechanical; D031307:Vicia faba / Q000737:chemistry* / Q000378:metabolism
chemical_list: D020409:Molecular Motor Proteins; D010940:Plant Proteins; D000255:Adenosine Triphosphate