Different protofilament-dependence of the microtubule binding between MAP2 and MAP4.
To see a molecular basis of the difference in the microtubule binding between MAP2 and MAP4, we compared the binding of them onto microtubule and Zinc-sheet in the presence of various concentrations of NaCl. The Zinc-sheet is the lateral association of protofilaments arranged in an antiparallel fashion with alternatively exposed opposite surfaces, so that binding requiring adjacent protofilaments is restricted. While the salt-dependence of the MAP2 desorption was not altered between these tubulin polymers, MAP4 dissociated from Zinc-sheet at lower concentrations of NaCl than from microtubule. These results suggest that single protofilament is sufficient for microtubule binding of MAP2 as observed by Al-Bassam et al. [J. Cell Biol. 157 (2002) 1187], but MAP4 appeared to interact with adjacent protofilaments during microtubule-binding. Weakened binding on Zinc-sheets was also observed in the projection domain-deletion mutants of MAP4, so that the difference in the protofilament-dependence would lie in the relatively conserved microtubule-binding domain.
Division of Biological Sciences, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Aya
A
Kawachi
Koji
K
Ichihara
Shin-ichi
S
Hisanaga
Junko
J
Iida
Hitoshi
H
Toyota
Hirokazu
H
Hotani
Tomohiko J
TJ
Itoh
D000818:Animals; D001665:Binding Sites; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism*; D011392:Proline / Q000032:analysis; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D012965:Sodium Chloride / Q000494:pharmacology
D008869:Microtubule-Associated Proteins; D012965:Sodium Chloride; D011392:Proline