[Accessibility of sulfhydryl groups to 5,5'-dithiobis-2-nitrobenzoic acid and acid-base properties of bovine and walleye pollock rhodopsin preparations].
Both the number of exposed SH-groups and the rate of reaction with 5,5'dithiobis-2-nitrobenzoic acid (DTNB) in walleye pollock and bovine rhodopsin depend on a degree of native structure of the preparation to be investigated. The preparations studied can be arranged in the order of increase of these parameters as follows: ROS less than rhodopsin extracted by digitonin less than triton X-100 less than cetyltrimethylammonium bromide (CTAB) less than sodium dodecylsulphate (SDS). After illumination of ROS and digitonin, triton X-100 and CTAB-solubilized rhodopsin, and increase was observed in the number of modified SH-groups. Dark and bleached samples of walleye pollock rhodopsin exhibited a faster rate reaction and a more number of modified SH-groups as compared to bovine preparation. The differences between bovine and walleye pollock preparation disappeared after complete opsin unfolding as a result ROS solubilization in SDS. Six SH-groups per molecule of rhodopsin were modified in both preparation under these conditions. No differences in the number of cysteine residues (10--11), disulfide groups (2), acid (35--40) and base (25--30) titratable groups per rhodopsin molecule were found between bovine and walleye pollock ROS membranes. The isoelectric point of both rhodopsin preparations was within the pH range 5.2--5.6. After proteolysis of ROS with papain, a fragment with molecular weight 24500 +/- 1000 was detected, which contained the same number of SH-groups and cysteine residues as in the case of intact rhodopsin. The results obtained suggest that, in spite of a similar primary structure, the walleye pollock visual pigment has more "loose" and "fluid" space packing in the ROS membrane than the bovine pigment.
D000818:Animals; D002417:Cattle; D002593:Cetrimonium Compounds; D055598:Chemical Phenomena; D002621:Chemistry; D004072:Digitonin; D004228:Dithionitrobenzoic Acid; D005399:Fishes; D006863:Hydrogen-Ion Concentration; D008027:Light; D009579:Nitrobenzoates; D010206:Papain; D010786:Photoreceptor Cells; D011092:Polyethylene Glycols; D012168:Retinal Pigments; D012243:Rhodopsin; D012967:Sodium Dodecyl Sulfate; D013438:Sulfhydryl Compounds
D002593:Cetrimonium Compounds; D009579:Nitrobenzoates; D012168:Retinal Pigments; D013438:Sulfhydryl Compounds; D012967:Sodium Dodecyl Sulfate; D011092:Polyethylene Glycols; D012243:Rhodopsin; D004228:Dithionitrobenzoic Acid; D010206:Papain; D004072:Digitonin
Izuchenie dostupnosti sh-grupp 5,5-ditiobis-2-nitrobenzoínoí kislote i kislotno-oshovnykh svoístv razlichnykh preparatov podopsina.