Structural characterization of
KKT4, an unconventional microtubule-binding kinetochore protein.
Structure 2021;
29:1014-1028.e8. [PMID:
33915106 PMCID:
PMC8443799 DOI:
10.1016/j.str.2021.04.004]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 02/17/2021] [Accepted: 04/08/2021] [Indexed: 01/01/2023]
Abstract
The kinetochore is the macromolecular machinery that drives chromosome segregation by interacting with spindle microtubules. Kinetoplastids (such as Trypanosoma brucei), a group of evolutionarily divergent eukaryotes, have a unique set of kinetochore proteins that lack any significant homology to canonical kinetochore components. 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 characterize 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 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. Taken together, these results provide structural insights into the unconventional kinetoplastid kinetochore protein KKT4.
Structures of microtubule-binding and BRCT domains in KKT4 are reported
The microtubule-binding domain consists of a coiled coil and a disordered tail
KKT4 interacts with microtubules via a basic surface at the coiled-coil N terminus
KKT4 has a phosphopeptide-binding BRCT domain
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