Pressure-induced dissociation of ribosomes and elongation cycle intermediates. Stabilizing conditions and identification of the most sensitive functional state.

Pressure-induced dissociation of ribosomes has been considered a major reason for the inhibition of protein biosynthesis and, hence, bacterial growth at high hydrostatic pressure [Jaenicke, R. (1981) Annu. Rev. Biophys. Bioeng. 10, 1-67]. We reexamined the issue, using a buffer system with polyamines that has been optimized to reproduce in-vivo-like performance of protein biosynthesis in vitro. By slightly modifying this buffer, we were able to find conditions that stabilize functional ribosomal complexes against the dissociating effect of pressure up to 100 MPa and uncharged tight couples up to 60 MPa. Approaching the physiological conditions by reducing the Mg2+ concentration down to 4 mM, one finds a significant destabilization of the post-translocational complex, which represents the most pressure-sensitive intermediate of the elongation cycle and is possibly the limiting factor for the pressure-induced block of protein biosynthesis and bacterial growth.