MODULATION OF MICROTUBULE SHAPE IN-VITRO BY HIGH-MOLECULAR-WEIGHT MICROTUBULE-ASSOCIATED PROTEINS MAP1A, MAP1B, AND MAP2

The effect of microtubule associated proteins on microtubule shape has been investigated in reconstitution experiments using purified tubuli n and purified MAP1A, MAP1B, and MAP2. Microtubules assembled in the p resence of these MAPs were fixed with 0.1% glutaraldehyde and, after n egative staining, were examined by electron microscopy, The results sh ow that MAP1A microtubules were generally short and 'straight' while t hose assembled with MAP1B were longer and 'bendy'. MAP2 microtubules s howed both types of morphologies even though straight microtubules wer e more abundant. These data suggest that MAPs may modulate not only mi crotubule dynamics but also microtubule shape which may be important i n their spatial distribution and/or role in specific neuronal areas.