Abstract
The kinetochore is the macromolecular protein machinery that drives chromosome segregation by interacting with spindle microtubules. Unlike most other eukaryotes that have canonical kinetochore proteins, a group of evolutionarily divergent eukaryotes called kinetoplastids (such as Trypanosoma brucei) have a unique set of kinetochore proteins. To date, KKT4 is the only kinetoplastid kinetochore protein that is known to bind microtubules. Here we use X-ray crystallography, NMR spectroscopy, and crosslinking mass spectrometry to characterise the structure and dynamics of KKT4. We show that its microtubule-binding domain consists of a coiled-coil structure followed by a positively charged disordered tail. The crystal structure of the C-terminal BRCT domain of KKT4 reveals that it is likely a phosphorylation-dependent protein-protein interaction domain. The BRCT domain interacts with the N-terminal region of the KKT4 microtubule-binding domain and with a phosphopeptide derived from KKT8. Finally, we show that KKT4 binds DNA with high affinity. Taken together, these results provide the first structural insights into the unconventional kinetoplastid kinetochore protein KKT4.
Competing Interest Statement
The authors have declared no competing interest.