Catching the Conformational Wave: Tuning the Working Strokes of Protofilaments as They Curl Outwards from Disassembling Microtubule Tips

Disassembling microtubules provide the driving forces behind chromosomal movement in dividing cells. This motion can occur independently of any conventional motor activity, and instead relies on tenacious attachment kinetochores to their dynamic microtubule substrates. During disassembly, thousands tubulin subunits are lost from tip per second even under tension, must maintain crumbling substrate. Despite recent advances our structural functional understanding microtubules, it is still unknown how these molecular machines sustain attachment. One popular hypothesis suggests curling oligomers (called protofilaments) at tips capture elements kinetochore physically pull along as they peel outwards body. Using a feedback-controlled optical trap assay, we recently showed that protofilaments spring-like, during “power-stroke”, release approximately four-fold energy required explain motility (Driver, 2017). Here use similar assay adapted for with bovine study effect magnesium protofilament curl properties mechano-chemical released by disassembling tips. Our results confirm be enlarged addition magnesium, observed some earliest electron microscopy microtubules. We find magnesium-based enlargement an increase show this independent disassembly speed, establish basis testing long-standing conformational wave tenacity kinetochore-microtubule interface.