Selective associations of hormonal steroids with aminoacyl transfer RNAs and control of protein synthesis

The hormonal steroids progesterone, estradiol, testosterone, and 5alpha-dihydrotestosterone bind to aminoacyl-tRNA, but not to deacylated tRNA, implying that a change in conformation of tRNA occurs on aminoacylation. Binding is restricted to a few tRNA species and depends on the structure of both tRNA and steroid. There is one binding site per aminoacyl-tRNA molecule, the specificity of which appears to depend on a restricted, single-stranded loop sequence and on the tRNA conformation. By binding to an aminoacyl-tRNA, a steroid can control polypeptide synthesis in a model in vitro system by inhibiting chain elongation under conditions where aminoacyl-tRNA concentration is rate-limiting.