Comparative Studies of Amino Acid Incorporation in a Cell‐free System from Psychrophilic <i>Pseudomonas</i> sp.412

Abstract

A subcellular amino acid incorporating system has been obtained from the psychrophilic bacterium Pseudomonas sp. 412. The system is active from near 0° to 45°, i. e. about 15° above the maximal growth temperature of the organism. The Mg 2+ requirement of the system increases from 7 mM at 2° to 14–18 mM at 45°. The sedimentation properties and optical density melting profiles of ribosomes from Pseudomonas sp. 412 have been found similar to those of Escherichia coli ribosomes. The poly U‐induced leucine incorporation is negligible in this system as compared to the E. coli and Bacillus stearothermophilus systems. The ribosomes and supernatant fractions of Pseudomonas sp. 412 and E. coli are interchangeable at 30–45° in the poly U‐promoted phenylalanine incorporation. At 2–9° only Pseudomonas sp. 412 ribosomes are active with both supernatant fractions. The ability to perform protein synthesis near 0° is related to ribosomal specificity. The E. coli soluble enzymes are active near 0° if combined with the ribosomes from the psychrophilie strain.