title: Analysis of the alphaB-crystallin domain responsible for inhibiting tubulin aggregation.
abstract: The cytoskeleton has a unique property such that changes of conformation result in polymerization into a filamentous form. alphaB-Crystallin, a small heat shock protein (sHsp), has chaperone activities for various substrates, including proteins constituting the cytoskeleton, such as actin; intermediate filament; and tubulin. However, it is not clear whether the "alpha-crystallin domain" common to sHsps also has chaperone activity for the protein cytoskeleton. To investigate the possibility that the C-terminal alpha-crystallin domain of alpha-crystallin has the aggregation-preventing ability for tubulin, we constructed an N-terminal domain deletion mutant of alphaB-crystallin. We characterized its structural properties and chaperone activities. Far-ultraviolet (UV) circular dichroism measurements showed that secondary structure in the alpha-crystallin domain of the deletion mutant is maintained. Ultracentrifuge analysis of molecular masses indicated that the deletion mutant formed smaller oligomers than did the full-length protein. Chaperone activity assays demonstrated that the N-terminal domain deletion mutant suppressed heat-induced aggregation of tubulin well. Comparison of chaperone activities for 2 other substrates (citrate synthase and alcohol dehydrogenase) showed that it was less effective in the suppression of their aggregation. These results show that alphaB-crystallin recognizes a variety of substrates and especially that alpha-crystallin domain binds free cytoskeletal proteins. We suggest that this feature would be advantageous in its functional role of holding or folding multiple proteins denatured simultaneously under stress conditions.
authors: Department of Life Sciences, The Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
authors: Eri
authors: E
authors: Ohto-Fujita
authors: Yoshinobu
authors: Y
authors: Fujita
authors: Yoriko
authors: Y
authors: Atomi
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism; D000818:Animals; D002021:Buffers; D002950:Citrate (si)-Synthase / Q000378:metabolism; D007700:Kinetics; D050505:Mutant Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D020836:Protein Structure, Quaternary / Q000187:drug effects; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D013552:Swine; D014404:Tubulin / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D002021:Buffers; D050505:Mutant Proteins; D010446:Peptide Fragments; D014404:Tubulin; D038203:alpha-Crystallin B Chain; D000426:Alcohol Dehydrogenase; D002950:Citrate (si)-Synthase
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