The Schizosaccharomyces pombe EB1 homolog Mal3p binds and stabilizes the microtubule lattice seam.
End binding 1 (EB1) proteins are highly conserved regulators of microtubule dynamics. Using electron microscopy (EM) and high-resolution surface shadowing we have studied the microtubule-binding properties of the fission yeast EB1 homolog Mal3p. This allowed for a direct visualization of Mal3p bound on the surface of microtubules. Mal3p particles usually formed a single line on each microtubule along just one of the multiple grooves that are formed by adjacent protofilaments. We provide structural data showing that the alignment of Mal3p molecules coincides with the microtubule lattice seam as well as data suggesting that Mal3p not only binds but also stabilizes this seam. Accordingly, Mal3p stabilizes microtubules through a specific interaction with what is potentially the weakest part of the microtubule in a way not previously demonstrated. Our findings further suggest that microtubules exhibit two distinct reaction platforms on their surface that can independently interact with target structures such as microtubule-associated proteins, motors, kinetochores, or membranes.
Sandblad
Linda
L
Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
Busch
Karl Emanuel
KE
Tittmann
Peter
P
Gross
Heinz
H
Brunner
Damian
D
Hoenger
Andreas
A
D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D008868:Microtubule Proteins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008961:Models, Structural; D017239:Paclitaxel / Q000494:pharmacology; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000378:metabolism*
C108851:Mal3 protein, S pombe; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D029702:Schizosaccharomyces pombe Proteins; C004805:5'-guanylylmethylenebisphosphonate; D006160:Guanosine Triphosphate; D017239:Paclitaxel