Zinc binding to human lactogenic hormones and the human prolactin receptor

Zinc half sites are present in all human lactogenic hormones: human prolactin (hPRL), growth hormone (hGH), placental lactogens (hPL) and the hPRL receptor (hPRLr). The influence of divalent zinc (Zn2+) as measured by intrinsic fluorescence or FRET in each of these hormones is unique and is affected by the presence of varying stoichiometries of hPRLr. These data show that both Zn2+ and hPRLr binding influence hPRL conformers in an interdependent fashion. Although each of these three lactogenic hormones bind hPRLr and induce a biological response that is sensitive to the presence of increasing concentrations of Zn2+, each hormone is unique in the mechanistic details of this process.