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Biology of Reproduction, Vol 24, 661-669, Copyright © 1981 by Society for the Study of Reproduction
1 Departments of Physiology, Biochemistry, and Medicine,
Boston University School of Medicine,
Boston, Massachusetts 02118 Since our present studies and those of others suggested that hCG binds weakly to specific FSH
receptors, purification of FSH receptor was attempted with hCG affinity chromatography. Calf
testis FSH receptor was initially isolated with differential and sucrose gradient centrifugation.
Several particulate membrane fractions were isolated from sucrose density interfaces and two
displayed enriched specific FSH binding. One of those fractions, F1, was more enriched with both
specific FSH binding sites and the plasma membrane markers, 5nucleotidase and oubain-sensitive
Na+K+-ATPase activities, and appeared less contaminated with other subcellular fractions. Other
highly purified antierior pituitary hormones and hCG competed less than 1% as effectively as
highly purified FSH for specific receptors in that membrane fraction. Consequently, FSH receptor,
derived from the enriched F, particulate fraction, was solubilized with 1% Triton X-100 and
subjected to further purification with hCG affinity chromatography. Bound solubilized FSH receptor was eluted from the hCG-affinity bed with [125I]-FSH and
studied by nondissociating polyacrylamide gel electrophoresis. A major radioactive peak, consistent
with [125]-FSH-receptor complex, was observed and migrated with an Rf significantly different
from that for free [125I]-FSH. Moreover, when the solubilized FSH receptor was eluted from the
affinity column with 1 M NaCl and subjected to sodium dodecyl sulfate gel electrophoresis, one
major polypeptide band with an estimated MW of 134,000 was found along with six other faintly
staining bands. Those observations strongly suggest that specific FSH receptor may be purified
with hCG affinity chromatography.
2 Section of Endocrinology and Metabolism, Throndike Memorial Laboratory,
Boston City Hospital,
Boston, Massachusetts 02118
Accepted on November 20, 1980
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