S-100 proteins and microtubules: analysis of the effects of rat brain S-100 (S-100b) and ox brain S-100a0, S-100a and S-100b on microtubule assembly-disassembly.

Rat brain S-100 (S-100b) and ox brain S-100a0, S-100a and S-100b have been tested for their ability to control the assembly and disassembly of brain microtubule proteins in the presence of either Ca2+ or Zn2+, in vitro. In the presence of Ca2+, single S-100 isoforms have similar, if not identical, effects, i.e. they inhibit assembly and promote disassembly. In the presence of Zn2+ from 0.1 to 1 mM (free concentration), rat S-100 and ox S-100a and S-100b inhibit assembly, while S-100a0 is without effect. These data are briefly discussed in relation to the cellular localization of single S-100 isoforms in the brain.