Effect of mutations in three αB crystallin interactive domains on microtubule assembly, disassembly, and tubulin aggregation.

<p>The DAPI fluorescence of assembled microtubules, disassembled tubulin, and tubulin aggregates in the absence of αB crystallin mutants was normalized to 1.0. In the presence of wt αB crystallin, microtubule assembly increased, microtubule disassembly was unchanged, and tubulin aggregation decreased. In the presence of the R120G mutant, which contains a mutation of the Arg-120 residue in the ₁₁₃FISREFH<u>R</u>₁₂₀ interactive sequence of αB crystallin, microtubule assembly decreased and microtubule disassembly and tubulin aggregation were similar to wt αB crystallin. In the presences of the αAβ8 mutant, in which the β8 sequence ₁₃₁LTITSSLS₁₃₈ of αB crystallin was replaced with the β8 sequence of αA crystallin ₁₂₇SALSCLSS₁₃₄, microtubule assembly increased, microtubule disassembly decreased, and tubulin aggregation was unchanged relative to wt αB crystallin. In the presence of the C-terminal deletion mutant Δ155–165, microtubule assembly and disassembly were lower and tubulin aggregation was unchanged relative to wt αB crystallin. Mutagenesis of sequences in αB crystallin corresponding to the αB crystallin peptides that altered tubulin-microtubule dynamics confirmed the effects of the αB crystallin peptides on microtubule assembly/disassembly and tubulin aggregation.