The Orphan Kinesin PAKRP2 Achieves Processive Motility via a Noncanonical Stepping Mechanism

Allison M. Gicking, Pan Wang, Chun Liu, Keith J. Mickolajczyk, Lijun Guo, William O. Hancock, Weihong Qiu

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Phragmoplast-associated kinesin-related protein 2 (PAKRP2) is an orphan kinesin in Arabidopsis thaliana that is thought to transport vesicles along phragmoplast microtubules for cell plate formation. Here, using single-molecule fluorescence microscopy, we show that PAKRP2 is the first orphan kinesin to exhibit processive plus-end-directed motility on single microtubules as individual homodimers. Our results show that PAKRP2 processivity is achieved despite having an exceptionally long (32 residues) neck linker. Furthermore, using high-resolution nanoparticle tracking, we find that PAKRP2 steps via a hand-over-hand mechanism that includes frequent side steps, a prolonged diffusional search of the tethered head, and tight coupling of the ATP hydrolysis cycle to the forward-stepping cycle. Interestingly, truncating the PAKRP2 neck linker to 14 residues decreases the run length of PAKRP2; thus, the long neck linker enhances the processive behavior. Based on the canonical model of kinesin stepping, such a long neck linker is expected to decrease the processivity and disrupt the coupling of ATP hydrolysis to forward stepping. Therefore, we conclude that PAKRP2 employs a noncanonical strategy for processive motility, wherein a long neck linker is coupled with a slow ATP hydrolysis rate to allow for an extended diffusional search during each step without sacrificing processivity or efficiency.

Original languageEnglish (US)
Pages (from-to)1270-1281
Number of pages12
JournalBiophysical journal
Issue number7
StatePublished - Apr 2 2019

All Science Journal Classification (ASJC) codes

  • Biophysics


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