The long-range goals of the proposed research are to determine, at the molecular level, the structural adaptations that enable the tubulins of Antarctic fishes to polymerize at the low body temperatures (-2 to +2 C) experienced by these cold-adapted vertebrates, and to examine the dynamics of the fish microtubules. The specific objectives of this project are five in number: 1) to compare the assembly energetics of brain tubulins from Antarctic and temperate nototheniid fishes; 2) to clone and to sequence cDNAs (DNAs complementary to messenger RNAs) that encode the brain tubulins of Antarctic and temperate nototheniid fishes; 3) to determine the structures of tubulin genes from an Antarctic fish, and possibly from a temperate nototheniid; 4) to determine the structural features responsible for the functional differences between brain and egg tubulins of an Antarctic fish; and 5) to characterize the dynamic behaviors of Antarctic fish microtubules at low temperatures. Molecular- biological experiments will be performed on tubulin cDNAs and genes derived from the nucleic acids of the Antarctic cod, Notothenia coriiceps neglecta, and of its temperate congener, the New Zealand black cod, N. angustata. Additionally, the dynamics of Antarctic fish microtubules at low temperatures will be examined by video-enhanced light-microscopic methods. Comparison of the primary sequences and posttranslational modifications of tubulins from Antarctic fishes with those of tubulins from related temperate fishes and warm-blooded vertebrates should reveal the molecular interactions and structural features necessary for microtubule assembly at low temperatures. This work will provide valuable information concerning the structure of tubulin genes from an extreme Antarctic poikilotherm.
