CONFORMATION AND BIOLOGICAL-ACTIVITY OF ACIDIC RIBOSOMAL-PROTEINS FROM DIFFERENT ORGANISMS

Acidic ribosomal proteins L7L12 from Escherichia coli, A2 from Bacillus stearothermophilus, and HL20 from Halobacterium cutirubrum are considered analogous based on amino acid composition and are presumed to be involved in similar functions on the ribosome. The conformation of these proteins has been studied by circular dichroic spectroscopy and correlated with their ability to support polyphenylalanine synthesis in vitro. Only proteins L7L12 and A2 showed comparable biological activity and conformational responses to changes in various conditions (salts, denaturing agents, helix-promoting solvents, temperature). L7L12 and A2 have highly ordered secondary structures, 48 ± 5 and 40-65%, respectively. Data for A2 show a wide range because of the established spontaneous partial denaturation of this protein at room temperature. Protein HL20, on the other hand, could not restore protein synthesis activity to L12 depleted E. coli ribosomes and its conformation is characterized by a very low content of α-helices (18.5%). © 1979.