Cross-linking of microtubules by microtubule-associated proteins (MAPs) from the brine shrimp, Artemia.
Microtubules induced with taxol to assemble in cell-free extracts of the brine shrimp, Artemia, are cross-linked by microtubule-associated proteins (MAPs). When the MAPs, extracted from taxol-stabilized microtubules with 1 M-NaCl are co-assembled with purified Artemia or mammalian neural tubulin, reconstitution of cross-linking between microtubules occurs. The most prominent non-tubulin protein associated with reconstituted cross-linked microtubules has a molecular weight of 49,000 but we cannot yet exclude the possibility that other proteins may be responsible for the cross-linking. Cross-linkers are separated by varying distances while cross-linked microtubules, prepared under different conditions, are 6.9-7.7 nm apart. Cross-linking of microtubules by MAPs occurs whether MAPs are added to assembling tubulin or to microtubules, and it is not disrupted by ATP. The MAPs are heat-sensitive and do not stabilize microtubules to cold. Immunological characterization of Artemia MAPs on Western blots indicates that Artemia lack MAP 1, MAP 2 and tau. Our results clearly demonstrate that Artemia contain novel MAPs with the ability to cross-link microtubules from phylogenetically disparate organisms in an ATP-independent manner.
Campbell
E J
EJ
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
MacKinlay
S A
SA
MacRae
T H
TH
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001156:Artemia; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification / Q000648:ultrastructure*; D008870:Microtubules / Q000187:drug effects / Q000648:ultrastructure*; D008970:Molecular Weight; D017239:Paclitaxel
D000470:Alkaloids; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins; D017239:Paclitaxel