COMPARISON OF AXONEMAL PROTEINS FROM 2 SPECIES OF TETRAHYMENA - II - DIFFERENCE IN HEAT-STABILITY OF MICROTUBULES

Tetrahymena thermophila, a heat resistant species, could swim at a spe ed of about 60% of that of the control even after being incubated at 4 0 degrees C for 10 min, whereas Tetrahymena pyriformis did not show an y motility after thermal treatment at 40 degrees C for 5 min. We have found that more than 30% of tubulins are solubilized from the axonemes of T. pyriformis by heat treatment at 40 degrees C for 30 min, while less than 15% of the tubulins are solubilized in T. thermophila. Elect ron microscopic observations revealed selective solubilization of tubu lins from the B-microtubules of T. pyriformis by thermal treatment. Co mparative analysis of axonemal tubulin isotypes shows highly similar p rofiles between the two Tetrahymena. This suggests that the heat stabi lity of axonemal microtubules observed in T. thermophila is not due to the properties of the tubulin itself, but that other axonemal compone nts which protect the microtubules against heat denaturation. In summa ry, combination of the present results and our previous findings on dy nein (Takaya et al. Comp. Biochem. Physiol. 1995;112B:727-32) show tha t T. thermophila, a heat tolerant species, installs heat resistant mic rotubules together with heat-stable dynein in order to adapt to a high temperature environment. (C) 1998 Elsevier Science Inc. All rights re served.