Protein Kinase Activity and Insulin-binding Activity in Plant Basic 7S Globulin

Komatsu, Setsuko; Koshio, Osamu; Hirano, Hisashi

doi:10.1271/bbb.58.1705

Cited by 29 publications

(24 citation statements)

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“…subunits. In Bg, we found a consensus sequence for a nucleotide-binding site, indispensable for protein phosphorylation [8], and a protein kinase activity which corresponds to about two thirds of the tyrosine kinase activity of the rat insulin receptor [9]. Furthermore, it was shown by immunocytochemistry that Bg is localized in the middle lamella of cell walls and the plasma membranes [lo].…”

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confidence: 99%

A Peptide that Stimulates Phosphorylation of the Plant Insulin‐Binding Protein

Watanabe

Barbashov

Komatsu

et al. 1994

European Journal of Biochemistry

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The soybean seed basic 7 s globulin (Bg) is capable of binding bovine insulin and insulin-like growth factors, and has protein kinase activity which corresponds to about two thirds of the tyrosine kinase activity of the rat insulin receptor. A 4-kDa peptide named leginsulin, which can bind to Bg and compete with insulin for binding to Bg, was isolated from radicles of germinated soybean seeds. The leginsulin had a stimulatory effect on the phosphorylation activity of Bg, suggesting that it is involved in cellular signal transduction. The leginsulin was sequenced by automated Edman degradation and electrospray ionization mass spectrometry. It consisted of 37 amino acid residues with six half-cystines in three disulfide bridges. The mass spectrometric analysis revealed that a portion of the peptide is processed to delete the C-terminal glycine like a number of animal peptide hormones, but not C-terminally amidated. The cDNA encoding the leginsulin was cloned, sequenced and considered to code for a precursor polypeptide consisting of a putative signal peptide, the leginsulin, a linker peptide, a 6-kDa peptide and a C-terminal peptide. Although there is no sequence similarity between the leginsulin and insulin or insulin-like growth factors, the leginsulin is a possible candidate for plant peptide hormones.The involvement of insulin-like polypeptides in regulatory metabolic mechanisms in plants and microorganisms is still under question. However, there is some information available on insulin-binding proteins within these organisms. In yeast, a plasma membrane protein was found to be capable of binding mammalian insulin [ l , 21. Recently, we have isolated a protein from soybean which bound insulin and insulin-like growth factor and which was found to be a seed basic 7 s globulin (Bg) [3,4]. In some other legume species and in carrot, related proteins were also shown to bind bovine insulin and insulin-like growth factors [4], suggesting that insulin-binding proteins are widely distributed in many plant species.Although amino acid sequence similarity was found in a limited region between Bg and the human insulin-binding protein [51], no sequence similarity was found between Bg and the human insulin-or insulin-like growth factor receptor [6, 71. However, Bg showed structural similarities to the insulin receptor in glycosylation, the presence of a cysteinerich domain and disulfide-bonded a and p (27 kDa and 16 kDa in Bg) subunits. Both proteins are also synthesized as larger precursor polypeptides which are post-translationally cleaved at the N-terminal side of a serine residue to generate a and j? subunits. In Bg, we found a consensus sequence for a nucleotide-binding site, indispensable for protein phosphorylation [8], and a protein kinase activity which corresponds to about two thirds of the tyrosine kinase activity of the rat insulin receptor [9]. Furthermore, it was shown by immunocytochemistry that Bg is localized in the middle lamella of cell walls and the plasma membranes [lo]. These results suggest that Bg may...

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confidence: 99%

A Peptide that Stimulates Phosphorylation of the Plant Insulin‐Binding Protein

Watanabe

Barbashov

Komatsu

et al. 1994

European Journal of Biochemistry

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“…43k-P also binds insulin and insulin-like growth factors, although there is no sequence similarity between 4k-P and insulin or insulin-like factors [118]. However, 43k-P has partial sequence homology with the human insulin-like growth factor-binding protein, and shares some functional and structural similarities with the insulin receptor [118]. 43k-P consists of four pairs of aand bsubunits linked by six disulfide bridges, with four glycosylation sites with asparagine-linked glycans, a putative transmembrane domain, and a conserved ATP-binding site.…”

Section: -Kda Peptidementioning

confidence: 99%

“…However, 43k-P has partial sequence homology with the human insulin-like growth factor-binding protein, and shares some functional and structural similarities with the insulin receptor [118]. Like the rat insulin receptor, 43k-P has protein tyrosine kinase activity, which is stimulated upon binding of 4k-P [115,118]. Like the rat insulin receptor, 43k-P has protein tyrosine kinase activity, which is stimulated upon binding of 4k-P [115,118].…”

Section: -Kda Peptidementioning

confidence: 99%

Plant Peptide Signals

Narváez-Vásquez

Orozco-Cárdenas

Pearce

2009

Amino Acids, Peptides and Proteins in Organic Chemistry

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“…Although the amino acid sequence shares significant sequence homology with a number of putative plant defence proteins, in particular with wheat xylanase inhibitors, neither physiological role in planta nor catalytic activity of c-conglutin have been proposed as yet (Scarafoni, Ronchi, & Duranti, 2010). A homologous soybean protein, termed Bg7S, was claimed to possess kinase activity and to interact with insulin (Komatsu, Koshio, & Hirano, 1994). However, no studies on the biological effects of this soybean protein have been carried out so far.…”

Section: Introductionmentioning

confidence: 99%