GETTING TO THE HEART OF BETA-TUBULIN

Cellular microtubules assemble and disassemble at a variety of rates a nd frequencies, and these properties contribute directly to the cell-c ycle-associated rearrangements of the microtubule cytoskeleton and to the molecular basis of mitosis. The kinetics of assembly/disassembly a re governed, in part, by the hydrolysis of GTP bound to the beta-tubul in nucleotide-binding site. The beta-tubulin GTP-binding site, therefo re, lies at the heart of microtubule assembly-disassembly kinetics, an d the elucidation of its structure is central to an understanding of t he cellular behaviour of microtubules. Unfortunately, the crystallogra phic structure of beta-tubulin is not yet available. In this review, w e describe the progress being made using mutagenesis and biochemical s tudies to understand the structure of this unusual GTP-binding site.