Pamlea J. Nelson

Molecular Weight and Hydrodynamic Properties of the Chromaffin Granule ATPase

Extraction of chroma5 granule membranes with the nonionic detergent C,,% in the presence of phosphatidyl serine (PS) solubilizes ATPase activity, which in the intact membrane is coupled to H+ pumping. Equilibrium sedimentation experiments performed in a table-top, air-driven ultracentrifuge indicate that the solubilized ATPase exists in a particle with roughly equal amounts (by weight) of protein and detergent. The particle partial specific volume, Vo), and total mass, m(o), were determined by sedimentation in media where various amounts of H,O were replaced with 40. Similar determinations were made for C&,-PS mix

Progesterone and Estradiol Modulate Interleukin-1β Messenger Ribonucleic Acid Levels in Cultured Human Peripheral Monocytes*

micelles. Gel atration of the solubilized ATPase gave a Stokes radius of 43 ? 4 A and an axial ratio of 1 was calculated. From the combined results of these sedimentation equilibrium and gel permeation chromatography studies, all of the major physical parameters of the C,,&-solubilized chroma& granule ATPase may be deduced. These are presented in TABLE 1. We have made the conventional assumption that the partial specific volume of the protein element is 0.73 cm’/g. The large amount of detergent and lipid associated with the enzyme strongly suggests that it is closely associated with the lipid bhyer by hydrophobic interactions.