Charge properties of human pituitary and amniotic fluid prolactins.
The apparent isoelectric points (pI) in isoelectric focusing (IF) of human pituitary and amniotic fluid prolactin (hPRL), both non-iodinated and iodinated, were determined. Unresolved mixtures of pituitary hPRL isohormones E and F, and of at least five isohormones found in amniotic fluid, and plasma hPRL exhibit an average pI value of 6.5 - 6.7. Transient state pH values observed or previously reported for hPRL components range from pH 5.9 to 6.8 after correction to standard conditions. At pH 8.1, the major isohormone, hPRL-F, carriers a charge of 2.2 net protons per molecule. The net charge differences among isohormones E, F and G are compatible with acquisition or loss of single charged groups per 20,000 molecular weight. This net charge is similar to that of the least prolactin-bioactive major isohormone of human growth hormone (hGH-B), while the hGH with a bioactivity comparable to that of hPRL exhibits a net charge of 3.4 valence units. The "large" isohormones J and H increased net charges, by a factor of 2-3, in direct proportion to their size increments.
D000653:Amniotic Fluid / Q000032:analysis*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D007774:Lactation; D010902:Pituitary Gland / Q000032:analysis*; D011247:Pregnancy; D011388:Prolactin / Q000097:blood / Q000276:immunology; D011863:Radioimmunoassay
D011388:Prolactin