Motility systems

Langford, G.M. (1995). Actin- and microtubule-dependent organelle motors Interrelationship between the twp motility systems. Curr. Opin. Cell Biol. 7,82-88. 

Huxley, H. E., Sliding filaments and molecular motile systems. J. Biol. Chem. 265 8347-8352, 1990. 

Kuroda, K. 1964. The behaviour of naked cytoplasmic drops isolated from plant cells. In Allen, R. D. and Kamiya, N. (Eds.), Primitive Motile Systems in Cell Biology. Academic Press, New York, 31-41... 

Inone S. Organization and Function of the Mitotic Spindle, in Primitive Motile Systems. In Cell Biology. Allen RD, Kamiya K, eds. 1964. Academic, New York. 

Diverse motors. Skeletal muscle, eukaryotic cilia, and bacterial flagella use different strategies for the conversion of free energy into coherent motion. Compare and contrast these motility systems with respect to (a) the free-energy source and (b) the number of essential components and their identity. 

Gerisch G, Noegcl AA, Schleicher M. Genetic alteration of proteins in actin-based motility systems. Annu Rev Physiol 1991 53 607-28. 

Comparison of Actin-Based and Tubulin-Based Motility Systems... 

In all the actin-based motility systems, and especially skeletal, cardiac and smooth muscle, contraction is initiated primarily by an increase in cytoplasmic [Ca +]. However, the major differences in histology and function of these muscle types are associated with great variety in how contraction is controlled. Smooth muscle especially differs from the model presented for skeletal muscle. Skeletal muscle is activated by Ca + released from SR in response to sarcolemmal action potentials. Ca + exerts its effect by binding to troponin on the thin filaments, which reverses the tropomyosin inhibition of cross-bridge formation. 

A class of motile systems completely different from and unrelated to the actin-myosin contractile systems is used in cellular structures as diverse as the mitotic spindle, protozoan and sperm flagella, and nerve axons. These systems are constructed from microtubules, very long, tubular structures built from a helical wrapping of the protein tubulin (Figure 8.19). There are two kinds of tubulin subunits, oi and each of molecular weight 55,000. They are present in equimolar quantities in the microtubule, which can be considered a helical array of ot-/i dimers. Alternatively, we can view the microtubule as consisting of 13 rows, or protofilaments, of alternating ot and subunits. Because the oi and b units are asymmetrical proteins, with a defined and reproducible orientation in the fiber, the microtubule has a definite sense of direction. 

MaurieUo, E. M., and Zusman, D. IL (2007) Polarity of motility systems in Myxococcus xan-thus. Curr. Opin. Microbiol. 10, 624-629. 

Shi, W.Y. and Zusman, D.R. (1993). The two motility systems of Myxococcus xanthus show different selective advantages on various surfaces. Proc. Natl. Acad. Sci. U.S.A. 90, 3378-3382. 

Here, as elsewhere in cell biology, rich interconnections between problems have long been obvious or may now be inferred. In this review, some attention is given to the relations between mitotic phenomena and these other areas of study reversible self-assembly of protein aggregates, other motile systems and the burgeoning information on microtubules, interactions between DNA and proteins, and the recently discovered, very different chromosome motion and distribution mechanisms in lower organisms. 

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