Osmolytes protect mitochondrial F0F1-ATPase complex against pressure inactivation

We have previously reported that carbohydrates and polyols protect differen t enzymes against thermal inactivation and deleterious effects promoted by guanidinium chloride and urea. Here, we show that these osmolytes (carbohyd rates, polyols and methylamines) protect mitochondrial F0F1-ATPase against pressure inactivation. Pressure stability of mitochondrial F0F1-ATPase comp lex by osmolytes was studied using preparations of membrane-bound submitoch ondrial particles depleted or containing inhibitor protein (IP). Hydrostati c pressure in the range from 0.5 to 2.0 kbar causes inactivation of submito chondrial particles depleted of IP (AS particles). However, the osmolytes p revent pressure inactivation of the complex in a dose-dependent manner, rem aining up to 80% of hydrolytic activity at the highest osmolyte concentrati on. Submitochondrial particles containing IP (MgATP-SMP) exhibit low ATPase activity and dissociation of IP increases the hydrolytic activity of the e nzyme. MgATP-SMP subjected to pressure (2.2 kbar, for 1 h) and then preincu bated at 42 degreesC to undergo activation did not have an increase in acti vity. However, particles pressurized in the presence of 1.5 M of sucrose or 3.0 M of glucose were protected and after preincubation at 42 degreesC, sh owed an activation very similarly to those kept at 1 bar. In accordance wit h the preferential hydration theory, we believe that osmolytes reduce to a minimum the surface of the macromolecule to be hydrated and oppose pressure -induced alterations of the native fold that are driven by hydration forces . (C) 2001 Elsevier Science B.V. All rights reserved.