Mechanochemical coupling of two coupled kinesin monomers: comparison with that of the single dimer

Abstract

The dynamics of cargo transport by two coupled kinesin monomers, such as kinesin-1, kinesin-2 and kinesin-3, is studied theoretically and is compared with that by the corresponding single dimer on the basis of our proposed model for the mechanochemical coupling of the two coupled monomers and that of the single dimer. It is shown that if the stalk, which connects the monomer and cargo, has a short length L_S (e.g., L_S < 5 nm) the cargo transport by the two monomers can be efficient with an unloaded velocity that can be similar to that by the corresponding single dimer, whereas the cargo transport by the two monomers with a long L_S can only be inefficient with an unloaded velocity and a stall force much smaller than those with the short L_S. Although the unloaded velocity for the two coupled kinesin-1 monomers with a short L_S can be similar to that for the single kinesin-1 dimer, the stall force for the former is reduced by about 2 times relative to that for the latter. The dynamics of the two coupled kinesin-3 KIF1A monomers relative to the single kinesin-3 dimer is similar to that of the two coupled kinesin-1 monomers relative to the single kinesin-1 dimer. By contrast, the stall force for the two kinesin-2 KIF3A monomers with a short L_S can be similar to that for the single kinesin-2 KIF3AA, KIF3BB or KIF3AB dimer. The theoretical results agree well with the available experimental evidence. The underlying mechanism of the two coupled kinesin-1 or kinesin-3 monomers with the short L_S having an evidently smaller stall force than the corresponding single dimer and the two coupled kinesin-2 KIF3A monomers with the short L_S having a stall force similar to that of the corresponding single dimer is explained.