EXTREME THERMOSTABILITY OF TARANTULA HEMOCYANIN

Biotops with extreme temperatures such as deserts force animals to avo id or escape high temperatures by biochemical, behavioural or morpholo gical adaptation. In this context we tested the resistance to heat of the oxygen carrier hemocyanin from the ancient tarantula Eurypelma cal ifornicum, which is found in arid zones of North America. Differential scanning calorimetry, light scattering, crossed immunogelelectrophore sis and oxygen binding experiments show that the 24-meric hemocyanin i s conformationally stable and fully functioning at temperatures up to 90 degrees C. Our results demonstrate that the cation-mediated state o f oligomerization is not only crucial for the high cooperativity of ox ygen binding of this hemocyanin, but also for its extreme stability in the physiological temperature and pH range.