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J M Maturo

Publications and source records attributed to J M Maturo.

16 recordsLinked to original sources
PubMed1985

Receptors for insulin and epidermal growth factor: interaction with organomercurial agarose.

The receptor for both insulin and epidermal growth factor (EGF) from human placental membranes, after crosslink labeling with 125I-labeled insulin and EGF, can be absorbed to an organomercurial-agarose derivative (Affi-Gel 501) and can be recovered from the gel by elution with dithiothreitol (DTT). Pretreatment of crosslink-labeled membranes with N-ethylmaleimide (NEM) blocks the ability of the receptor to react with the organomercurial column. NEM also abolishes the protein kinase activity of both receptors. Under appropriate conditions, insulin can promote the reaction of the insulin receptor with the organomercurial-agarose derivative. For both the insulin and EGF receptors, our results provide an avenue for the isolation of the sulfhydryl-containing receptor domains that may play a role in the control of receptor function.

Chromatography, Affinity↗
PubMed1985

Distinct hydrodynamic forms of the insulin receptor: electrophoretic analysis of the RI and RII species.

In previous work, we identified two insulin receptor species, RI (KAV = 0.31) and RII (KAV = 0.53), that could be separated by gel filtration on Sepharose 6B. In the present study, we sought to establish that these two receptor species do represent larger (RI) and smaller (RII) oligomeric forms of the receptor, rather than representing receptor species separated from each other by differential adsorption to the Sepharose matrix. Receptor solubilized from isolated human placenta membranes was purified by lectin- and insulin-agarose chromatography and was radiolabeled with carrier-free 125I. The labeled receptor was separated by Sepharose 6B gel filtration into two fractions (peak I, KAV = 0.31; peak II, KAV = 0.53), was immunoprecipitated by anti-insulin receptor antibody, and was analysed by electrophoresis in nonreducing polyacrylamide slab gels. The autoradiograms of the gels indicated that peak I (KAV = 0.31, RI receptor form) contained a number of receptor species of 240 000 daltons or greater, whereas peak II (KAV = 0.53, RII receptor form) contained mainly receptor species of 210 000 daltons or smaller. In particular, large amounts of a 90 000 dalton species (presumably free receptor beta-subunit) were present in peak II. Incubation of the material obtained from peak I with insulin resulted in a change in the electrophoretic pattern, which became identical with that observed for material recovered from peak II.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Membrane↗
PubMed1983

Receptors for insulin and basic somatomedin: immunological and affinity-chromatographic cross-reactivity.

Human placental receptors for insulin and for human basic somatomedin (BSM, analogous to human insulinlike growth factor I (IGF-I] were selectively cross-link labelled with 125I-labelled insulin and BSM using disuccinimidyl suberate under conditions whereby cross-linking of 125I-labelled insulin to the BSM receptor and of 125I-labelled BSM to the insulin receptor was avoided. We have found that the cross-link-labelled receptors for insulin and BSM, present in equivalent amounts in human placenta membrane preparations, both cross-react with antibodies directed against purified rat liver insulin receptor. Compared with the human insulin receptor, the BSM receptor cross-reacted with the antireceptor antibody to a level of roughly 9%, indicating a limited sequence homology between the insulin and BSM receptors. Since both receptors are present in comparable amounts in solubilized placenta membrane preparations, we sought methods for the selective purification of both receptors from such extracts, so as to provide a basis for further comparative structural studies of the two receptors. We have observed that both receptors were adsorbed by affinity columns of insulin-agarose, in a manner that did not yield insulin receptor entirely free from the BSM receptor. As an alternative for receptor purification, we have found that immunoaffinity columns using antiligand antibody should provide a means for the selective isolation of cross-link labelled receptor from tissues in which both are present in equivalent amounts.

Chromatography, Affinity↗
PubMed1978

Insulin receptor: interaction with nonreceptor glycoprotein from liver cell membranes.

In crude receptor preparations (either particulate or soluble) of rat liver membranes, the insulin receptor exhibits complicated binding kinetics (two binding plateaus, half-saturated at approximately 60 pM and 700 pM insulin) and an apparent chromatographic heterogeneity, suggested by the presence of two detectable, soluble insulin-binding components with apparent Stokes radii of 72 A and 38 A. In contrast, the insulin receptor isolated by affinity chromatography exhibits a simple binding isotherm (half-maximal saturation of binding at 700 pM insulin) without evidence for negative cooperativity and behaves as a single component (apparent Stokes radius of 38 A) upon chromatography on Sepharose 6B. The apparent discrepancies between the properties of the unpurified insulin receptor and the affinity-purified receptor can be attributed to the presence in crude preparations of a nonreceptor constituent(s) having properties consistent with those of a membrane glycoprotein. A glycoprotein fraction from such crude soluble membrane preparations, freed from insulin receptor and subsequently partially purified using concanavalin-A-agarose, when combined with affinity-purified insulin receptor, causes both a reappearance of the complicated binding kinetics and an increase in the receptor's apparent Stokes radius from 38 A to 72 A. Similar results are observed for a glycoprotein fraction obtained from rat adipocyte membranes but are not observed for an identical fraction isolated from human erythrocyte membranes. We conclude that the insulin receptor in rat liver membranes can interact with another nonreceptor membrane glycoprotein that may represent either a nonrecognition moiety of the receptor oligomer or an effector molecule to the biological action of insulin.

Adipose Tissue↗