On the hand-over-hand mechanism of kinesin

Abstract

We present here a simple theoretical model for conventional kinesin. The model reproduces the hand-over-hand mechanism for kinesin walking to the plus end of a microtubule. A large hindering force induces kinesin to walk slowly to the minus end, again by a hand-over-hand mechanism. Good agreement is obtained between the calculated and experimental results on the external force dependence of the walking speed, the forward͞backward step ratio, and dwell times for both forward and backward steps. The model predicts that both forward and backward motions of kinesin take place at the same chemical state of the motor heads, with the front head being occupied by an ATP (or ADP,P i ) and the rear being occupied by an ADP. The direction of motion is a result of the competition between the power stroke produced by the front head and the external load. The other predictions include the external force dependence of the chemomechanical coupling ratio (e.g., the stepping distance͞ATP ratio) and the walking speed of kinesin at force ranges that have not been tested by experiments. The model predicts that the chemomechanical coupling remains tight in a large force range. However, when the external force is very large (e.g., Ϸ18 pN), kinesin slides in an inchworm fashion, and the translocation of kinesin becomes loosely coupled to ATP turnovers.backward walking ͉ chemomechanical coupling K inesins are linear motors that are widely distributed in almost all eukaryotic cells, and there are 45 different kinesin species in humans (1). These microtubule-based motors are involved in many functions of biological systems, including cargo transport, mitosis, and control of microtubule dynamics, and they play important roles in signal transduction pathways (1-5). Kinesins are further classified into three categories: N-terminal kinesins, C-terminal kinesins, and M kinesins, with the first being the majority in humans (2). The motions of the kinesins on microtubules are directional: N-terminal kinesins move to the plus end of the microtubule, and C-terminal kinesins move toward the minus end of the microtubule (1, 2). Kinesins have a large variety of structures, and they function as monomers, dimers, or tetramers in cells (1, 2). Among the family members of kinesins, the only conserved region is the catalytic core (5).Conventional kinesin is a homodimer, and each of the monomers contains a heavy chain of Ϸ120 kDa (1). The essential structural elements of a kinesin monomer include an N-terminal motor head, which contains the nucleotide-binding site, a neck linker, a long coiled coil that is responsible for dimerization, and a globular cargo-binding tail domain formed by a light chain (1, 2, 5). The motor domain also contains the microtubule-binding site. In forming a dimer, the long coiled coils form a central stalk. The neck linker is an extension from the motor head and is assumed (1, 3, 4) to serve as a lever arm in force generation. Structural studies indicate that the conformation of the neck linkers changes in a nucleotide-dependent m...

Statistical properties of the dichotomous noise generated in biochemical processes

“…Joining a specific nanometry technique with fluorescence microscopy, they showed that the myosin head can make several steps along the actin filament per ATP molecule hydrolyzed [21,22]. This observation was confirmed in some other laboratories for myosin [23], dynein [24,25] and kinesin [26]. In Fig.…”

Identification of a strong binding site for kinesin on the microtubule using mutant analysis of tubulin

“…Previous measurements of the mechanical properties of two‐headed kinesin indicated that the kinesin stall force might be determined by (1) the binding affinity of the head to the microtubule in the strongly bound state and (2) the ATP‐binding kinetics to the nucleotide‐free head (Visscher et al , 1999; Nishiyama et al , 2002; Lakämper and Meyhöfer, 2005; Shao and Gao, 2006). Thus, the kinesin stall force exerted on the mutated microtubules with reduced affinity for kinesin in AMP‐PNP state is expected to be smaller than that exerted on the wild‐type microtubules.…”

“…Although the structural elements that determine the shape of the binding potential for strong binding have not been fully identified, the measurement of the stall force demonstrated that the size of the stall force was linearly related to the unbinding force for minus‐end loading, but it was independent of the unbinding force for plus‐end loading (Figure 5C). As predicted from the analyses of the force‐velocity relationship of single kinesin molecule (Visscher et al , 1999; Nishiyama et al , 2002; Carter and Cross, 2005; Lakämper and Meyhöfer, 2005; Shao and Gao, 2006), for two‐headed kinesin to produce force, it might be crucial for the trailing head in the strong binding state to sustain against the load imposed towards the minus‐end direction. Our result is the first direct demonstration that the stall force is directly related to the stability of the strong binding state.…”

“…These independent interfaces might be the structural basis for the physicochemical properties distinct for each chemical state. In the ADP state, mobility freedom of the motor has to be ensured to a certain extent while it is loosely anchored to the microtubule surface (Okada and Hirokawa, 2000; Wang and Sheetz, 2000; Sosa et al , 2001; Skiniotis et al , 2004; Lakämper and Meyhöfer, 2005), whereas in the AMP‐PNP state, the motor has to be tightly attached to the microtubule so that it can sustain load (Visscher et al , 1999; Kawaguchi and Ishiwata, 2001; Nishiyama et al , 2002; Uemura et al , 2002; Shao and Gao, 2006).…”

Mechanical control of the directional stepping dynamics of the kinesin motor

“…Recent singlemolecule (SM) experiments have shown that, with each stepping motion being strongly coupled to the ATP, the kinesin moves toward the (ϩ) ends of MTs by taking discrete 8-nm steps (3-7) in a hand-over-hand fashion (4,7,8). Although the ultimate understanding of kinesin's motility is still far from completion, the SM experiments (3)(4)(5)(6)(7)(8)(9), together with the series of kinetic ensemble measurements (10)(11)(12)(13) and theoretical studies (14)(15)(16)(17)(18)(19), begin providing glimpses to the physical principle of how kinesin walks.…”