Interaction between calmodulin and microtubule-associated proteins prepared at different stages of brain development.

Rat brain microtubules were prepared at the adult stage and from immature (i.e., 4-day-old) animals. At an early stage of development, the composition of microtubule-associated proteins is qualitatively different from that found at the adult stage [(1982) Eur. J. Biochem. 129, 465-471]. The influence of calmodulin on the time course of assembly of second cycle microtubules was compared at both stages of brain development (i.e., microtubules originating from 4-day-old and adult animals). In the presence of Ca2+ the inhibition of microtubule assembly was more pronounced at a young stage of brain development than at the adult stage. Cross-linking studies with 125I-labeled calmodulin further established that the two major microtubule-associated proteins, MAP2 and TAU were able to bind to calmodulin at both stages of brain development but with different intensities. The labeling with 125I-labeled calmodulin was Ca2+-dependent, specific, displaced by unlabeled calmodulin and trifluoperazine.