Molecular Adaptation of Microtubules
and Microtubule Motors from Antarctic Fish
H. William Detrich, III
Department ofBiology, Northeastern University, Boston, MA 02115, USA
Introduction
Temperature, through its effects on the equilibria and kinetics of weak,
noncovalent molecular interactions, plays an important role in governing
enzyme activity and controlling macromolecular assembly reactions.
Microtubule assembly, an example of the latter, entails the formation of a
cylindrical polymer composed of a~-tubulin dimers and decorated by the
heterogeneous microtubule-associated proteins (MAPs). Polymerization is
entropically driven and mediated in part by the release of structured water
from sites of intersubunit contact [1]. As a consequence, microtubule
formation in vitro by the tubulins and MAPs of homeotherms is highly
sensitive to thermal perturbation, with assembly favored by physiological
temperatures near 37°C and depolymerization caused by lower temperatures
«15 0q. Similarly, the microtubule motors (dyne ins and kinesins) of
mesophiles (e.g., mammals), which are mechanochemical enzymes that use
the energy released upon ATP hydrolysis to produce directed movement
along microtubules, display little activity at psychrophilic temperatures.
Thus, one may ask, "How have the microtubule proteins of cold-living
ectotherms evolved to function efficiently at low temperatures?"
The coastal fish of the Antarctic, which now experience body temperatures
between -1.86 °C (the freezing point of seawater) and ~ +2 °C, diverged from
temperate osteichthyans approximately 38 million years ago as the Southern
Ocean began to cool [2]. The teleostean suborder Notothenioidei, which is
largely endemic to the Antarctic, provides numerous cold-adapted species
suitable to biochemical, physiological, and molecular-biological analysis. To
learn about the evolutionary adaptations of microtubule systems, my
laboratory has been studying the microtubule proteins of two Antarctic
rockcods, Notothenia coriiceps and Gobionotothen gibberifrons and an
icefish, Chionodraco rastrospinosus. In this review, I summarize our current
understanding of microtubule cold adaptation and place our results in the
context of related work on microtubules from mesophilic organisms.
G. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer-Verlag Italia 1998
and Microtubule Motors from Antarctic Fish
H. William Detrich, III
Department ofBiology, Northeastern University, Boston, MA 02115, USA
Introduction
Temperature, through its effects on the equilibria and kinetics of weak,
noncovalent molecular interactions, plays an important role in governing
enzyme activity and controlling macromolecular assembly reactions.
Microtubule assembly, an example of the latter, entails the formation of a
cylindrical polymer composed of a~-tubulin dimers and decorated by the
heterogeneous microtubule-associated proteins (MAPs). Polymerization is
entropically driven and mediated in part by the release of structured water
from sites of intersubunit contact [1]. As a consequence, microtubule
formation in vitro by the tubulins and MAPs of homeotherms is highly
sensitive to thermal perturbation, with assembly favored by physiological
temperatures near 37°C and depolymerization caused by lower temperatures
«15 0q. Similarly, the microtubule motors (dyne ins and kinesins) of
mesophiles (e.g., mammals), which are mechanochemical enzymes that use
the energy released upon ATP hydrolysis to produce directed movement
along microtubules, display little activity at psychrophilic temperatures.
Thus, one may ask, "How have the microtubule proteins of cold-living
ectotherms evolved to function efficiently at low temperatures?"
The coastal fish of the Antarctic, which now experience body temperatures
between -1.86 °C (the freezing point of seawater) and ~ +2 °C, diverged from
temperate osteichthyans approximately 38 million years ago as the Southern
Ocean began to cool [2]. The teleostean suborder Notothenioidei, which is
largely endemic to the Antarctic, provides numerous cold-adapted species
suitable to biochemical, physiological, and molecular-biological analysis. To
learn about the evolutionary adaptations of microtubule systems, my
laboratory has been studying the microtubule proteins of two Antarctic
rockcods, Notothenia coriiceps and Gobionotothen gibberifrons and an
icefish, Chionodraco rastrospinosus. In this review, I summarize our current
understanding of microtubule cold adaptation and place our results in the
context of related work on microtubules from mesophilic organisms.
G. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer-Verlag Italia 1998