DYNAMIC INSTABILITY OF MICROTUBULES FROM COLD-LIVING FISHES

The dynamic instability of microtubules free of microtubule-associated proteins from two genera of cold-living fishes was measured, by means of video-enhanced differential-interference-contrast microscopy, at t emperatures near those of their habitats. Brain microtubules were isol ated from the boreal Atlantic cod (Gadus morhua; habitat temperature a pproximate to 2-15 degrees C) and from two austral Antarctic rockcods (Notothenia gibberifrons and N. coriiceps neglecta; habitat temperatur e approximate to -1.8 to +2 degrees C). Critical concentrations for po lymerization of the fish tubulins were in the neighborhood of 1 mg/ml, consistent with high interdimer affinities. Rates of elongation and f requencies of growth-to-shortening transitions (''catastrophes'') for fish microtubules were significantly smaller than those for mammalian microtubules. Slow dynamics is therefore an intrinsic property of thes e fish tubulins, presumably reflecting their adaptation to low tempera tures. Two-dimensional electrophoresis showed striking differences bet ween the isoform compositions of the cod and the rockcod tubulins, whi ch suggests that the cold-adapted microtubule phenotypes of northern a nd southern fishes may have arisen independently. (C) 1994 Wiley-Liss, Inc.