The 'assembly-promoting sequence region' of microtubule-associated protein 4 failed to promote microtubule assembly.
In order to study the function of the bovine MAP4 microtubule-binding domain (the assembly-promoting (AP) sequence region), a fragment corresponding to the AP sequence region was prepared using an Escherichia coli expression system. When the fragment was mixed with purified tubulin at 37 degrees C, the fragment caused a time- and dose-dependent turbidity increase, and the fragment bound to tubulin. However, the products were cold-stable, and amorphous aggregates were observed by electron microscopy. Using axonemes as the seeds for microtubule assembly, the microtubule-elongating activity of the fragment was examined. A dose-dependent turbidity increase of the sample was observed, and electron microscopic observation revealed that microtubules were dose-dependently elongated from the axonemes. Consequently, the AP sequence region does not nucleate microtubules, but elongates them.
Katsuki
M
M
Department of Biochemical Engineering and Science, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Japan. mc9607@bse.kyutech.ac.jp
Tokuraku
K
K
Nakagawa
H
H
Murofushi
H
H
Kotani
S
S
D000302:Adrenal Cortex / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D003001:Cloning, Molecular; D004926:Escherichia coli; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D014404:Tubulin / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure
D000596:Amino Acids; D008869:Microtubule-Associated Proteins; D011994:Recombinant Proteins; D014404:Tubulin