Comparison between the human serum growth hormone-binding protein and the water-soluble growth hormone-binding site released from IM-9 lymphocytes.
The characteristics of the human serum growth hormone-binding protein (GHBP) were compared with those of a water-soluble GH-binding site prepared by incubating cultured IM-9 lymphocytes in assay buffer with 25 mmol/l iodoacetamide. High-performance liquid chromatography gel filtration of the water-soluble GH-binding site incubated with 125I-labeled human GH ([125I]hGH) revealed a large peak of bound [125I]hGH eluting at the same position as the peak of [125I]hGH bound to the GHBP in serum. The estimated M(r) of the peak was 120,000, presumably representing one [125I]hGH bound to two binding sites. The binding specificities of the serum GHBP, the water-soluble GH-binding site and the GH receptor on IM-9 lymphocytes were identical. The binding affinities for 22,000 hGH and for 20,000 hGH of the serum GHBP were similar to the binding affinity of the water-soluble GH-binding site but lower than those of the cellular GH receptor. These findings show that the characteristics of the serum GHBP are comparable to those of the water-soluble GH-binding site released from IM-9 cells and support the hypothesis that in man the serum GHBP is produced by proteolytic cleavage of the cellular GH receptor.
Massa
G
G
Department of Paediatrics, University of Leuven, Belgium.
Ilondo
M
M
Vanderschueren-Lodeweyckx
M
M
D001665:Binding Sites; D002352:Carrier Proteins / Q000097:blood*; D002460:Cell Line; D003470:Culture Media / Q000378:metabolism; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism; D006801:Humans; D007460:Iodoacetamide / Q000494:pharmacology; D008214:Lymphocytes / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000378:metabolism*; D012995:Solubility; D014867:Water
D002352:Carrier Proteins; D003470:Culture Media; D011986:Receptors, Somatotropin; D014867:Water; D013006:Growth Hormone; C051815:somatotropin-binding protein; D007460:Iodoacetamide