Assertion: microtubule's end | /r/HasProperty | exposed at −end
Facets:
Source sentences:
text: Each protofilament is a longitudinal head-to-tail assembly of αβ-tubulin heterodimers (tubulins), resulting in structurally polar microtubules, with β-tubulin facing the (+) end and α-tubulin being exposed at the (−) end.