Characterization of molybdate-stabilized estrogen receptors by hydrophobic interaction HPLC: resolution of two 8S subunits

This report describes the separation and characterization of estrogen receptors (ER) according to their degree of hydrophobicity and surface charges. Molybdate-stabilized [3H]ER from rabbit uterine cytosol was sequentially purified by passage through a size-exclusion pre-column, an anion-exchange column, and a hydrophobic interaction column. With fresh cytosol, a major radioactive peak was eluted from the DEAE columns; a major peak and a minor, less hydrophobic, peak were eluted from the hydrophobic column. In contrast, ER from frozen cytosol showed one peak in the DEAE-column and exhibited four radioactive peaks in the hydrophobic column. By sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis, [3H] tamoxifen aziridine(TA)-labelled ER showed radioactive bands at 62 and 48 kd. The subunits which were characterized by these radioactive bands were successfully separated by the hydrophobic column; the more hydrophobic subunit corresponded to the 62 kd band. The HPLC-purified [3H]TA-labelled ER subunits sediment at a 7.4-8.5S region in a low-salt sucrose gradient. These results show that differential negative surface charge and hydrophobic areas exist in the holo-receptor and its subunits, and the hydrophobic interaction HPLC column separates the two major 8S steroid binding subunits of ER.     

THE EFFECTS OF RELATIVE HUMIDITY AT THE TIME OF FLOWERING ON FRUIT SET IN BEAR OAK (QUERCUS ILICIFOLIA)

Fifty-six randomly selected bear oak trees were moved into growth chambers to determine the influence of relative humidity at the time of flowering on fruit set. The effect of humidity greater than 61 % was to greatly reduce fruit set. Trees which were kept in a chamber where relative humidity was less than 50 % had significantly higher fruit set.