Analysis of the steroid binding domain of rat androgen-binding protein.
The site-directed photoaffinity ligand [3H]17 beta-hydroxy-4,6-androstadien-3-one (delta 6-testosterone) was used to label the steroid binding domain of rat androgen-binding protein (rABP). After digestion with trypsin, the major radiolabeled peptide was isolated by reverse phase chromatography. The peptide was found to have the following amino acid sequence: Ile Ala Leu Gly Gly Leu Leu Leu Pro Thr Ser. Gaps in the sequence that one would anticipate if delta 6-testosterone formed an adduct with a single amino acid were not encountered. Several different amino acids appear to have been labeled as expected given the free radical nature of photoactivated delta 6-testosterone. The sequence obtained corresponded to a tryptic peptide (amino acids 171-181) of the rABP precursor. The only other protein having this amino acid sequence was human sex hormone binding globulin. The binding domain lies in a hydrophobic pocket that contains a predicted beta-sheet and turn secondary structure, as would be anticipated given the hydrophobic nature of the steroid molecule. A hydropathy and secondary structure analysis of rABP was performed as a basis for discussing the results of the current study in relation to previous studies on the steroid binding domain on human sex hormone binding globulin.
Danzo
B J
BJ
Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2633.
Parrott
J A
JA
Skinner
M K
MK
D000345:Affinity Labels; D000595:Amino Acid Sequence; D000727:Androgen-Binding Protein / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010777:Photochemistry; D011487:Protein Conformation; D051381:Rats; D012738:Sex Hormone-Binding Globulin / Q000737:chemistry; D013739:Testosterone / Q000031:analogs & derivatives / Q000378:metabolism; D014357:Trypsin
D000345:Affinity Labels; D000727:Androgen-Binding Protein; D010446:Peptide Fragments; D012738:Sex Hormone-Binding Globulin; C023630:6-dehydrotestosterone; D013739:Testosterone; D014357:Trypsin