Insights into Antiparallel Microtubule Crosslinking by PRC1, a Conserved Nonmotor Microtubule Binding Protein

SummaryFormation of microtubule architectures, required for cell shape maintenance in yeast, directional cell expansion in plants and cytokinesis in eukaryotes, depends on antiparallel microtubule crosslinking by the conserved MAP65 protein family. Here, we combine structural and single molecule fluorescence methods to examine how PRC1, the human MAP65, crosslinks antiparallel microtubules. We find that PRC1's microtubule binding is mediated by a structured domain with a spectrin-fold and an unstructured Lys/Arg-rich domain. These two domains, at each end of a homodimer, are connected by a linkage that is flexible on single microtubules, but forms well-defined crossbridges between antiparallel filaments. Further, we show that PRC1 crosslinks are compliant and do not substantially resist filament sliding by motor proteins in vitro. Together, our data show how MAP65s, by combining structural flexibility and rigidity, tune microtubule associations to establish crosslinks that selectively “mark” antiparallel overlap in dynamic cytoskeletal networks.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (167 K)Download as PowerPoint slideHighlights► Human MAP65, PRC1 uses structured and unstructured microtubule binding domains ► PRC1 is flexible on one microtubule but rigid when crosslinking two filaments ► PRC1 crosslinks do not substantially resist kinesin-5 driven filament sliding ► Compliant PRC1 crosslinks can dynamically track antiparallel microtubule overlap