Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.32 (bromelain)
 1,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Microsomal membranes form human placenta, which bind 5-20 pmol of 125I-epidermal growth factor (EGF) per mg protein, have been affinity-labeled with 125I-EGF either spontaneously or with dimethylsuberimidate. Coomassie blue staining patterns on SDS polyacrylamide gels are minimally altered, and the EGF-receptor complex appears as a specifically labeled band of 180,000 daltons which is not removed by urea, neutral buffers, or chaotropic salts but is partially extracted by mild detergents. Limited proteolysis by alpha chymotrypsin and several other serine proteases yields labeled fragments of 170,000, 130,000, 85,000, and 48,000 daltons. More facile cleavage by papain or bromelain rapidly degrades the hormone-receptor complex to smaller labeled fragments of about 35,000 and 25,000 daltons. These fragments retain the binding site for EGF, are capable of binding EGF, and remain associated with the membrane. Alpha chymotryptic digestion of receptor solubilized by detergents yields the same fragments obtained with intact vesicles, suggesting that the fragments may represent intrinsic proteolytic domains of the receptor.
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PMID:Proteolytic domains of the epidermal growth factor receptor of human placenta. 626 4

Elucidation of the three-dimensional structure of the complex of the epidermal growth factor (EGF) and its receptor is essential for understanding the molecular mechanisms of the EGF-receptor interaction and EGF-induced receptor-receptor interaction. NMR is useful to investigate interactions in solution between macromolecules at atomic resolution, but has a limitation in molecular masses of target proteins: less than 300 residues. We have prepared a fragment with apparent molecular mass of 40 kDa in SDS gels from the soluble extracellular domain of the EGF receptor (sEGFR, 619 residues) by sequential limited proteolysis with proteinase K and bromelain. This fragment is a monomeric structural domain consisting of 202 amino acid residues (Cys302-Arg503) and 18-kDa sugar chains, and binds EGF and transforming growth factor-alpha (TGF alpha). This 40-kDa domain has a dissociation constant of about 1 microM for human TGF alpha, which is similar to that of the parental sEGFR. sEGFR oligomerizes in response to EGF and TGF alpha, while the 40-kDa domain does not, suggesting that the sequences other than this domain is required for receptor oligomerization. The 40-kDa ligand-binding domain described in this report is suitable for analysis by various physico-chemical approaches such as NMR.
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PMID:A 40-kDa epidermal growth factor/transforming growth factor alpha-binding domain produced by limited proteolysis of the extracellular domain of the epidermal growth factor receptor. 842 Sep 71