Somatomedin receptor of human placenta: solubilization, photolabeling, partial purification, and comparison with insulin receptor - PubMed (original) (raw)

Comparative Study

Somatomedin receptor of human placenta: solubilization, photolabeling, partial purification, and comparison with insulin receptor

B Bhaumick et al. Proc Natl Acad Sci U S A. 1981 Jul.

Abstract

Using a recently isolated human basic somatomedin (basic SM) similar to insulin-like growth factor I (IGF-I), we studied both the photoaffinity-labeled and unlabeled basic-SM receptor solubilized from human placental cell membranes. Unlike the result with the insulin receptor, high yields of soluble basic-SM-binding activity are obtained with Triton X-100. The soluble basic-SM receptor retains high-affinity (Kd approximately 0.3 nM) peptide-specific binding of basic SM, similar to the binding present in particulate placenta membranes; the receptor exhibits a comparatively low affinity for insulin (Kd approximately 3 microM). On Sepharose 6B, like the crude soluble insulin receptor, the basic-SM receptor migrates as a species with an apparent Stokes radius of 7.2 nm; unlike the insulin receptor, the basic-SM receptor does not, under similar conditions, yield a smaller binding species (apparent Stokes radius 3.8 nm). Upon photoaffinity labeling with 125I-labeled basic SM, one principal specifically labeled constituent is detected. Upon gel electrophoresis in the presence of 2-mercaptoethanol, the photolabeled constituent, like the insulin receptor, migrates as a species with an apparent molecular weight of about 140,000; in the absence of reducing agent, a molecular weight greater than 240,000 is observed. Lectin-agarose affinity chromatography yields a 30-fold purification both of the basic-SM-binding activity and the photolabeled constituent. Anti-insulin receptor antibody does not appear to precipitate the basic-SM receptor. We conclude that the basic-SM receptor of human placenta is a glycoprotein, remarkably similar to (an isoreceptor) but distinct from the insulin receptor previously characterized in this tissue.

PubMed Disclaimer

Similar articles

Cited by

References

    1. Proc Natl Acad Sci U S A. 1972 May;69(5):1277-81 - PubMed
    1. Biochem Pharmacol. 1973 Dec 1;22(23):3099-108 - PubMed
    1. J Clin Endocrinol Metab. 1974 Aug;39(2):283-92 - PubMed
    1. Biochem Biophys Res Commun. 1974 Dec 11;61(3):957-62 - PubMed
    1. Adv Protein Chem. 1976;30:251-451 - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources