Polarity of dynein-microtubule interactions in vitro: Cross-bridging between parallel and antiparallel microtubules

Abstract

Ciliary doublet microtubules produced by sliding disintegration in 20 μM MgATP2- reassociate in the presence of exogenous 30S dynein and 6 mM MgSO4. The doublets form overlapping arrays, held together by dynein cross-bridges. Dynein arms on both A and B subfibers serve as unambiguous markers of microtubule polarity within the arrays. Doublets reassociate via dynein cross-bridges in both parallel and antiparallel modes. Although parallel interactions are favored 2:1. When 20 μM ATP is added to the arrays, the doublets undergo both vanadat-sensitive and insensitive forms of secondary disintegration to reproduce the original population of doublets. The results demonstrate that both parallel and antiparallel doublet cross-bridging is sensitive to dissociation by ATP even though normal ciliary motion depends strictly on dynein interactions between parallel microtubules.