Isolation, purification and study of membrane proteins: 1. Complete purification and properties of spinach chloroplast cytochrome b-559. 2. A medium and procedure for the non-destructive solubilisation of membrane proteins.

A rational methodology for the purification and study of active, undenatured membrane proteins is described. Using these methods cytochrome b559, a relatively "delicate", tightly-bound membrane protein, was completely purified from spinach chloroplast grana membranes with high overall recovery. Pure cytochrome b559 was a lipoprotein complex containing 41% protein and 56 (±6) % lipid (consisting of four distal lipids). It contained 8 small polypeptide subunits (mol. wt. = 5,600 ± 1,000 Daltons) per molecule (monomer). A method is described for the complete, non-destructive solubilisation of membrane proteins. This method was successfully used with beef heart mitochondria, spinach chloroplast grana, red cell ghosts, mouse Ehrlich ascites tumour cell membranes and Pseudomonad B-16 bacterial membranes. Eight cytochromes and four enzyme activities were shown to be quantitatively stable in the medium used. No protein was encountered which was irreversibly inactivated by the medium. Resolution of the proteins is described. The discovery of "autoreduction" of pure cytochrome f is reported. It was shown to be a light-dependent phenomenon inhibited by the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1, 1-dimethyl urea. A method is described for the essay of microgram quantities of the nonionic detergent Triton X-l00.Une méthodologie rationelle pour la purification et l'étude des protéines membranaires à l'état actif et non-dénaturé est décrite. Utilisant ces méthodes, le cytochrome b559, protéine assez délicate et liée solidement aux membranes a été purifiée complètement à partir de membranes grana de chloroplastes d'épinards avec un rendement total élevé. Le cytochrome b559 pur est un complexe lipoprotéinique contenant 41% de protéines et 56% (±6%) de lipides, qui consistent en quatre lipides distincts. Il contient huit petites sous-unités polypeptidiques ayant un poids moléculaire de 5600 ± 1000 Daltons par molécule (monomer). Une méthode est décrite pour la solubilisation complète et non-destructive des protéines membranaires. [...

Immunomodulation in humans caused by beta-carotene and vitamin A

Carotenoids and retinoids can stimulate some human immune responses. These include cytoine release with anti-tumor cell activity, increased natural killer cells and activated lymphocytes after both in vitro and in vivo treatment with beta carotene. Such stimulations seem only partly due to retinoids formed from carotenoid metabolism and may be due to effects caused by the structure of beta carotene. Changes in immune functions could explain in part the cancer resistance provided by high carotenoid or retinoid intakes in animals. © 1990 Pergamon Press plc

Immunomodulation in humans caused by beta-carotene and vitamin A

Carotenoids and retinoids can stimulate some human immune responses. These include cytoine release with anti-tumor cell activity, increased natural killer cells and activated lymphocytes after both in vitro and in vivo treatment with beta carotene. Such stimulations seem only partly due to retinoids formed from carotenoid metabolism and may be due to effects caused by the structure of beta carotene. Changes in immune functions could explain in part the cancer resistance provided by high carotenoid or retinoid intakes in animals. © 1990 Pergamon Press plc