**3.1. Tubulin**

Tubulin binds with high affinity to cellular membranes, and bound to mitochondrial membranes represent ~ 2% of total cellular tubulin [25]. It is important for ensuring intracellular transport and DNA segregation in cell division. Rostovtseva et al. [19] have found induction of fast, reversible blockade of VDAC conductance by tubulin at nanomolar concentration in 1–100 ms range. Closing occurs in concentration-dependent manner and negative potential as low as 5 mV. The type of VDAC, phosphorylation level, and membrane lipid composition have an impact on VDAC blocking. Change in channel selectivity in blocked state results in impermeability to ATP [26]. The restriction of ATP/ADP and other respiratory substrates fluxes leads to reduction of oxidative phosphorylation and promotion of apoptosis. Therefore, signals that enhance VDACtubulin binding by kinase-regulated phosphorylating VDAC or by increasing the concentration of available free tubulin in the cytosol would reduce mitochondrial respiration [27].
