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Forisomes are ATP-independent, Ca2+-driven contractile protein bodies acting as reversible valves in the phloem of plants of the legume family. Forisome contraction is anisotropic, as shrinkage in length is associated with radial expansion and vice versa. To test the hypothesis that changes in length and width are causally related, we monitored Ca2+- and pH-dependent deformations in the exceptionally large forisomes of Canavalia gladiata by high-speed photography, and computed time-courses of derived geometric parameters (including volume and surface area). Soybean forisomes, which in the resting state resemble those of Canavalia geometrically but have less than 2% of the volume, were also …

Background and Aims Forisomes are Ca2+-dependent contractile protein bodies that form reversible plugs in sieve tubes of faboid legumes. Previous work employed Vicia faba forisomes, a not entirely unproblematic experimental system. The aim of this study was to seek to establish a superior model to study these intriguing actuators.

Methods Existing isolation procedures were modified to study the exceptionally large, tailed forisomes of Canavalia gladiata by differential interference contrast microscopy in vitro. To analyse contraction/expansion kinetics quantitatively, a geometric model was devised which enabled the computation of time-courses of derived parameters such as forisome volume from simple parameters readily determined …

The structural and functional analysis of biological macromolecules has reached a level of resolution that allows mechanistic interpretations of molecular action, giving rise to the view of enzymes as molecular machines. This machine analogy is not merely metaphorical, as bio-analogous molecular machines actually are being used as motors in the fields of nanotechnology and robotics. As the borderline between molecular cell biology and technology blurs, developments in the engineering and material sciences become increasingly instructive sources of models and concepts for biologists. In this review, we provide a – necessarily selective – summary of recent progress in the usage of …

This paper has no abstract; this is the first paragraph. Motility of cell components in both animal and plant cells is mostly based on the movement of motor proteins along actin filaments or microtubules [Boal, 2002]. The dominance of ATP hydrolysis as the energy source for such movements is so complete, that modern textbooks define “motor proteins” as nucleoside triphosphate-dependent actuators [e.g., Alberts et al., 2002]. In only one known case, a reversible mechanism of cell motility is driven by the interaction of Ca2+ and the responsive protein(s). Some sessile ciliates control the effective length of their stalk by means …