In mammals end-binding (EB) proteins family contain three members, EB1/2/3, which associate with the growing tips of microtubules and modulate their dynamics directly and indirectly, by recruiting essential factors to fine-tune microtubules for their many essential roles in cells. Previously EB proteins have been shown to recognize a stabilizing GTP/GDP-pi cap at the growing microtubules in vitro, serving as a marker of instantaneous microtubule stability. However, the fine structure and dynamics of the zone recognized by EB-proteins in live cells have not yet been examined in detail. It has been shown that, on average, EB3-RFP protein profiles on microtubules in murine fibroblasts remain unchanged. However, we found that in some cases the profile has a more complex structure, which differs from the classical representation. By complex form we mean the additional EB3-RFP protein intensity zone on the microtubule, which manifests itself on kymographs as characteristic stationary bands, which in turn can appear both in the microtubule body and near the main peak. We believe that this fact may indicate a more complex structure of the growing plus-end microtubules and GTP caps in particular.
End-binding protein, microtubule, GTP-tubulin
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