J. Biol. Chem., Vol. 260, Issue 27, 14636-14641, 11, 1985
Electrophoretic analysis of the estrogen receptor. Relationship of multiple receptor forms to the molybdate-stabilized form
JK Skipper, FI Davidson and TH Hamilton
The origin of and relationships among multiple forms of the estrogen
receptor from rat uteri were investigated using electrophoretic and
conventional hydrodynamic methods of analysis. Evidence is presented that
the molybdate-stabilized, multimeric receptor (Stokes radius approximately
70A; S20,w approximately 9.5 S; Mr approximately 290,000) corresponds to an
acidic form of the receptor that has relatively high electrophoretic
mobility. This discrete form, which appears to represent the untransformed
state that does not bind to DNA, was converted to a number of derived forms
by exposure to conditions that result in receptor transformation and/or
subunit dissociation. In crude cytosol, transformation always generated
receptor forms that were excluded from polyacrylamide gels, and it was
shown that these are large heterogeneous aggregates. This explains previous
failed attempts to analyze the receptor by polyacrylamide gel
electrophoresis. Transformation of partially purified, molybdate-stabilized
receptor never led to aggregate formation, but resulted instead in the
generation of two relatively basic estrogen-binding species of low
electrophoretic mobility. These components may represent the free or
dissociated estrogen-binding subunits. Together, the results suggest a
model for the molybdate-stabilized receptor wherein at least one of its
components is an acidic, nonestrogen-binding subunit.
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