Molecular motor proteins, fueled by energy from ATP hydrolysis, move along actin filaments or microtubules, performing work in the cell. The kinesin microtubule motors transport vesicles or organelles, assemble bipolar spindles or depolymerize microtubules, functioning in basic cellular processes. The mechanism by which motor proteins convert energy from ATP hydrolysis into work is likely to differ in basic ways from man‐made machines. Several mechanical elements of the kinesin motors have now been tentatively identified, permitting researchers to begin to decipher the (...) mechanism of motor function. The force‐producing conformational changes of the motor and the means by which they are amplified are probably different for the plus‐ and minus‐end kinesin motors. BioEssays 25:1212–1219, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

The cellular processes of transport, division and, possibly, early development all involve microtubule‐based motors. Recent work shows that, unexpectedly, many of these cellular functions are carried out by different types of kinesin and kinesin‐related motor proteins. The kinesin proteins are a large and rapidly growing family of microtubule‐motor proteins that share a 340‐amino‐acid motor domain. Phylogenetic analysis of the conserved motor domains groups the kinesin proteins into a number of subfamilies, the members of which exhibit a common molecular organization and (...) related functions. The kinesin proteins that belong to different subfamilies differ in their rates and polarity of movement along microtubules, and probably in the particles/organelles that they transport. The kinesins arose early in eukaryotic evolution and gene duplication has allowed functional specialization to occur, resulting in a surprisingly large number of different classes of these proteins adapted for intracellular transport of vesicles and organelles, and for assembly and force generation in the meiotic and mitotic spindles. (shrink)

A framework for understanding the complex movements of mitosis and meiosis has been provided by the recent discovery of microtubule motor proteins, required for the proper distribution of chromosomes or the structural integrity of the mitotic or meiotic spindle. Although overall features of mitosis and meiosis are often assumed to be similar in mechanism, it is now clear that they differ in several important aspects. These include spindle structure and assembly, and timing of chromosome segregation to opposite poles. Here we (...) review progress in the functional characterization of several newly identified microtubule motor proteins, emphasizing their possible roles in spindle structure and function. (shrink)