Hepatic progesterone receptors: characterization in the turtle Chrysemys picta.
High and low affinity progesterone (P)-binding proteins similar to those described in the chick oviduct were characterized for the first time in liver cytosol in an oviparous turtle, Chrysemys picta. Two forms of high affinity P receptor were separated by diethyl aminoethyl (DEAE)-Sepharose anion exchange chromatography; the A form eluted in low salt buffer, and the B form at a KCl concentration of 0.20 M in a linear gradient. After photoaffinity labeling of crude cytosol with [3H] R5020, two overlapping peaks of radioactivity were detected with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After separation with DEAE-Sepharose and photoaffinity labeling, the A form migrated as a single peak with a mol wt of 90,000, and the B form as a single peak with a mol wt of 123,000. The affinity (Kd, 2.9 X 10(-9) M), capacity (1 pmol/mg protein), and binding specificity were characteristic of a P receptor. P competed most effectively for [3H]P binding. R5020 and deoxycorticosterone were good competitors; 5 alpha-pregnenolone, 17 alpha-hydroxyprogesterone, and testosterone were quite effective; cortisol, corticosterone, aldosterone, and 5 alpha-dihydrotestosterone were poor competitors. A lower affinity P-binding component (Kd, 1 X 10(-7) M; maximum binding, 15 pmol/mg protein) co-eluted from DEAE-Sepharose columns with the A and B receptor forms. This is the first description of a hepatic P receptor in any vertebrate.
Riley
D
D
Biology Department, Boston University, Massachusetts 02215.
Reese
J C
JC
Callard
I P
IP
D000345:Affinity Labels; D000818:Animals; D001667:Binding, Competitive; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D010777:Photochemistry; D011374:Progesterone / Q000378:metabolism; D011397:Promegestone / Q000378:metabolism; D011980:Receptors, Progesterone / Q000302:isolation & purification / Q000378:metabolism*; D014426:Turtles / Q000378:metabolism*
D000345:Affinity Labels; D011980:Receptors, Progesterone; D011374:Progesterone; D011397:Promegestone