Vesikin, a vesicle associated ATPase from squid axoplasm and optic lobe, has characteristics in common with vertebrate brain MAP 1 and MAP 2.
Vesikin, a protein that can associate with squid axoplasmic vesicles or optic lobe microtubules, has been implicated as a force-generating molecule involved in microtubule-dependent vesicle transport [Gilbert and Sloboda, 1986, 1988]. Because vesikin crossreacts with an antibody to porcine brain microtubule associated protein 2 (MAP 2), studies were conducted to compare squid vesikin and brain MAPs. When taxol stabilized microtubules containing vesikin as a microtubule associated protein were incubated in the presence of ATP, vesikin dissociated from the microtubule subunit lattice. This behavior would be expected for an ATP-dependent, force generating molecule that serves as a crossbridge between vesicles and microtubules. When chick brain microtubules were treated under the same conditions, MAP 2 remained bound to the microtubules while MAP 1 dissociated in a manner similar to vesikin. One dimensional peptide mapping procedures revealed that, although digestion of vesikin and MAP 2 generated several peptides common to both proteins, vesikin and MAP 2 are clearly not identical. Furthermore, the addition of vesikin or MAPS 1 and 2 to purified tubulin stimulated microtubule assembly in a manner dependent on the concentration of added protein. These findings demonstrate that brain MAPs share characteristics common to squid vesikin and support the suggestion that brain MAPs 1 and 2 might act as a force generating complex for vesicle transport in higher organisms.
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Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755.
Sears
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Gilbert
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Sloboda
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D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001370:Axonal Transport; D001923:Brain Chemistry; D002645:Chickens; D049832:Decapodiformes / Q000378:metabolism*; D006358:Hot Temperature; D008869:Microtubule-Associated Proteins / Q000032:analysis*; D010449:Peptide Mapping; D013552:Swine
D008869:Microtubule-Associated Proteins; C057505:vesikin protein, squid; D000255:Adenosine Triphosphate