Inhibitory effects of poly(L-aspartic acid) on the assembly of brain microtubules and the interaction of microtubule-associated protein 2 with F-actin in vitro.
The effects of poly(L-aspartic acid) (PLAA) on microtubule assembly and microtubule-associated protein (MAP) 2-actin interaction were examined in vitro. PLAA inhibited assembly of rat brain microtubules and induced rapid disassembly of already formed microtubules. Inhibition was stronger by PLAA with a high molecular weight than that by low molecular weight. The ratios of 47 kDa PLAA to microtubule proteins causing 50% inhibition of the assembly and disassembly were 0.015 and 0.04 (w/w), respectively. Both MAP 1 and MAP 2 were bound to a PLAA-Sepharose 4B affinity column, while tubulin was not retained by the column. PLAA caused selective dissociation of MAP 1 and MAP 2 from microtubules polymerized by taxol. It is therefore concluded that PLAA interacts specifically with MAPs. PLAA also inhibited the MAP 2 induced cross-linking of actin filaments, showing an almost complete inhibition at a PLAA to MAP 2 ratio of 1:5,000 (w/w). Binding experiments of PLAA with digested MAP 2 by chymotrypsin using affinity chromatography and sedimentation experiments showed that PLAA was preferentially bound to a 35 kDa fragment which includes the microtubule- and actin-binding domain of the MAP 2 molecule. These results suggest that PLAA suppressed the functions of MAP 2 through a domain which is located in the 35 kDa fragment.
Nakamura
A
A
Department of Functional Polymer Science, Faculty of Textile Science and Technology, Shinshu University, Nagano.
Arai
T
T
Kondo
Y
Y
Fujii
T
T
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000648:ultrastructure*; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects*; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D014404:Tubulin / Q000378:metabolism
D000199:Actins; D008869:Microtubule-Associated Proteins; D010446:Peptide Fragments; D010455:Peptides; D014404:Tubulin; C017645:polyaspartate; D002918:Chymotrypsin