The processivity of kinesin-2 motors suggests diminished front-head gating.
Kinesin-2 motors, which are involved in intraflagellar transport and cargo transport along cytoplasmic microtubules, differ from motors in the canonical kinesin-1 family by having a heterodimeric rather than homodimeric structure and possessing a three amino acid insertion in their neck linker domain. To determine how these structural features alter the chemomechanical coupling in kinesin-2, we used single-molecule bead experiments to measure the processivity and velocity of mouse kinesin-2 heterodimer (KIF3A/B) and the engineered homodimers KIF3A/A and KIF3B/B and compared their behavior to Drosophila kinesin-1 heavy chain (KHC). Single-motor run lengths of kinesin-2 were 4-fold shorter than those of kinesin-1. Extending the kinesin-1 neck linker by three amino acids led to a similar reduction in processivity. Furthermore, kinesin-2 processivity varied inversely with ATP concentration. Stochastic simulations of the kinesin-1 and kinesin-2 hydrolysis cycles suggest that "front-head gating," in which rearward tension prevents ATP binding to the front head when both heads are bound to the microtubule, is diminished in kinesin-2. Because the mechanical tension that underlies front-head gating must be transmitted through the neck linker domains, we propose that the diminished coordination in kinesin-2 is a result of its longer and, hence, more compliant neck linker element.
Muthukrishnan
Gayatri
G
Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
Zhang
Yangrong
Y
Shastry
Shankar
S
Hancock
William O
WO
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D003198:Computer Simulation; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism; D006801:Humans; D016547:Kinesins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment
D029721:Drosophila Proteins; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; C525729:kinesin 2 protein, Drosophila; D016547:Kinesins