A biochemical mechanism for Stu2/XMAP215-family microtubule polymerases.

Stu2/XMAP215-family microtubule polymerases operate via an enzyme-like mechanism, with activity dependent on tubulin-binding TOG domains, revealing a convergent evolution in cytoskeletal regulation.

• Why it matters: Understanding the biochemical basis of microtubule dynamics is crucial for insights into cell division and motility, yet the mechanisms of polymerase activity remain unclear, limiting targeted interventions.
• What they did: The study applied an enzyme-like biochemical model to quantify how Stu2 activity relates to the number of TOGs and their tubulin-binding properties, using measurements of binding affinity and dissociation rates.
• The result: Findings show Stu2 functions as an efficient tubulin-shuttling antenna, with activity limited by tubulin:TOG association rate, providing a detailed mechanistic framework that highlights evolutionary parallels with actin polymerases.