Sub-cellular particles and the nicotinic acid hydroxylase system in extracts of Pseudomonas fluorescens KBi

Abstract

1.1. The distribution is described of nicotinic acid hydroxylase activity in sub-cellular fractions of Pseudomonas fluorescens KBi.2.2. In crushed cells, the bulk of the activity is localised on a structure resembling the cell wall and protoplast membrane of the cell. The remaining activity sediments at high centrifugal forces together with a RNA-containing particle having a sedimentation coefficient of approximately s 40.3.3. Activity is further subdivided in ultrasonically disrupted cells amongst poly-disperse components representing disintegrated portions of the cell wall-membrane structure.4.4. A purified 40-S particle fraction has been obtained by ultracentrifugation of an extract prepared by further mild disintegration of the cell wall-membrane fraction from crushed cells. The nature of the parent material and the origin of the particles is discussed.5.5. The 40-S preparations contain a lipoprotein complex and a ribonucleoprotein, separable by electrophoresis. Nicotinic acid hydroxylase and succinoxidase activity associated with these preparations is confined to the former material.6.6. Treatment of the intact cells with lysozyme and versene did not yield structures equivalent to protoplasts under appropriate conditions. The separated cell wall-membrane structure, however, is very susceptible to dissolution under this treatment. At 30°, nicotinic acid hydroxylase activity is liberated into a supernatant fraction not sedimented at 15,000 × g. At 0° the enzymic activity is still retained on the particulate fraction.