Figure 3.

Motor lattice-distribution and tip-accumulation on growing MTs. (A) Schematic drawing of the model, showing binding with rate α, motor motion with velocity v_m, motor dissociation with rate β, and MT growth with velocity v_g. In addition, motors can bind to the MT tip with rate α_t or they can walk into the MT tip via the MT lattice. At the MT tip, motors dissociate with rate β_t. (B) Average number of motors per 0.2 μm of MT lattice on a growing MT, including accumulation at the MT tip (according to Eqs. 9 and 12). Different shaded values correspond to density profiles at different time points. Parameters: α = 4 μm⁻¹ min⁻¹, β = 1/min, v_m = 4 μm/min, v_g = 2 μm/min, α_t = 0/min, and β_t = 2/min. (C) Motor accumulation at MT tip according to Eq. 12. Schematic drawings correspond to panel A. (Dotted line) The value n₀, i.e., the number of motors at infinite length. (Solid curve) Motor proteins bind only to the lattice and walk into the tip: α = 10 μm⁻¹ min⁻¹, β = 0.5/min, v_m = 3 μm/min, v_g = 2μm/min, α_t = 0/min, and β_t = 2/min. (Dashed curve) Motors bind only to the tip: α = 0, β = NA, v_m = 3 μm/min, v_g = 2 μm/min, α_t = 5/min, and β_t = 0.5/min.