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, bacteri al growth at high hydrostatic pressure [Jaenicke, R. (1981) Annu. Rev. Biophys. Bioeng. 10, 1-67]. We reexamined the issue, using a buffer s ystem with polyamines that has been optimized to reproduce in-vivo-lik e 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 phy siological conditions by reducing the Mg2+ concentration down to 4 mM, one finds a significant destabilization of the post-translocational c omplex, which represents the most pressure-sensitive intermediate of t he elongation cycle and is possibly the limiting factor for the pressu re-induced block of protein biosynthesis and bacterial growth.