Oscillations, Waves, and Interactions - GWDG

446 S. Lakämper and C. F. Schmidt
Figure 9. Schematic working hypothesis for the processive movement of Kinesin-1 Motors.
For details see text. (from Ref. [14]).
end – dimerize via an extended alpha-helical “coiled-coil” of about 60 nm length. This
rather rigid structure is interrupted by short stretches of disordered domains which
allow the dimer to fold internally, such that the most C-terminal domain, the tail,
and its bound kinesin light chains (KLC) can interact with the head and initial stalk
(also termed neck). This interaction serves as an internal energy saving mechanism,
as cargo also attaches through adapter molecules to the KLC and tail domains: when
there is no cargo bound the motor self-inhibits by back-folding to the head and thus
prevents futile ATP-consumption in the cell [13].
Kinesin-1 binds and transports cargoes such as vesicles over long distances, for
example through axons of nerve cells which can, in extreme cases, be 1 m in length.
Kinesin-1 dimers have structurally evolved to be able to bind to microtubules in
a cyclical, nucleotide-dependent manner such that one head remains bound to the
microtubule at any given time. This “processivity” is terminated in a statistical
manner (Poisson process), on average after about 100–150 cycles. With a spacing of
8 nm between kinesin binding sites on the microtubule lattice, a single motor dimer
can generate up to 7 pN force. Processivity ensures that cargo can be transported by
few motor molecules. Through single-molecule and biochemical assays a basic model
for Kinesin-1 stepping has emerged.