Temperature-dependency of poly(U)-directed polyphenylalanine synthesis was examined with different cell-free systems of
Vibrio sp. strain ABE-1, a psychrophile, and
Pseudomonas aeruginosa, a mesophile. In S-30 fractions, the activity of
V. ABE-1 was higher than that of
P. aeruginosa at and below 25°, but the activity of the former decreased rapidly above 25° and was completely lost at 40°. In ribosome-supernatant systems,
V. ABE-1 ribosomes, especially 50S subunits, served a cold-stabilizing function, but
V. ABE-1 supernatant was remarkably thermolabile, which was probably attributable to thermo-inactivation of phenylalanyl-tRNA synthetase present in the supernatant.
V. ABE-1 ribosomes had no activation factor able to be released by washing with 1M NH
4Cl.
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