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Perspectives in Biology and Medicine 45.2 (2002) 305-307



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Book Review

Mechanics of Motor Proteins and the Cytoskeleton


Mechanics of Motor Proteins and the Cytoskeleton. By Jonathon Howard. Sunderland, MA: Sinauer Associates, 2001. Pp. 367. $59.95.

Many types of biological movement are driven by "motor proteins" that move along two types of filament, actin and microtubules, that form the "cytoskeleton" which helps to maintain cell shape. The best understood of the motors is myosin, which forms the thick filaments that interact with actin filaments to produce muscle force and shortening. Other motor proteins include dyneins and kinesins, as well as non-muscle myosins. In addition to muscle contraction and amoeboid movement, these motors carry out such diverse tasks as the beating of cilia and the transport of vesicles within cells. To further compound the story, the cytoskeletal filaments are not just passive tracks; their polymerization drives a number of biological mechanisms, including the separation of chromosomes during mitosis, the intracellular movement of infectious agents, and protrusion of the acrosomal processes of some sperm.

The recent development of sophisticated micro-physical techniques for studying both the movement and the force developed by the individual motor [End Page 305] proteins and by filament polymerization has generated a large interest in this area and a growing body of research. Mechanisms of Motor Proteins and the Cytoskeleton, a short book by one of the masters in this area of science, puts the work into perspective, and anyone interested in beginning to learn about this new and fascinating area of biology would be well advised to read this book first. It is written as a text to be used in a biology course, and each chapter has problem sets that can be used by interested readers to sharpen their understanding. In addition, the first 40 percent of the book describes some of the physical principles used to define the motor movements. The general ideas will be familiar to anyone acquainted with elementary physics and chemistry, but the application of these principles to single molecules requires a different paradigm. An important example of this difference is the calculation of all quantities in dimensions applicable to single molecules. A major impediment to the union of chemistry and physics in the study of biological mechanics has been the difficulty of switching between chemical values, expressed in moles, and physical quantities expressed in dimensions applicable to larger structures. Workers in the new field have eliminated this difficulty by the simple expedient of expressing all quantities in units of the single molecule. Other examples of micro-physical principles important to this thinking include thermal agitation as the mechanism driving stochastic molecular reactions and the over-damping of most molecular movements.

It should also be emphasized that it is not necessary to master the physical principles outlined in the first part of the book to obtain a good comprehension of the proteins that follow. The descriptions of motors and filaments are sufficiently lucid that they can be read on their own, and the first part of the book can be regarded as "enrichment" material that the author wanted his classes to be familiar with. Undoubtedly, he goes into greater physical detail in his classes than is covered in the book.

The information about the motor proteins and filaments is not comprehensive but rather exemplary experimental discoveries and conclusions. These examples are sufficiently varied, however, that the reader will gain a solid overview of the entire field from the brief chapters. There are, nonetheless, two areas where the interested student will want to read further. The mechanically inclined will undoubtedly want to learn more about the methods used to measure molecular force and movement. These methods are at least as fascinating as the molecules themselves, and the descriptions in the book are sufficiently enticing that the curious will automatically begin asking how the measurements are made. Unfortunately, there is not yet a book that covers this area, and the reader will have go to the scientific literature for descriptions of the varied and imaginative ways that these experiments...

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