Proinsulin C-peptide interaction with protein tyrosine phosphatase 1B demonstrated with a labeling reaction |
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Authors: | Theres Jä gerbrink |
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Affiliation: | Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden |
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Abstract: | Based on nickel-catalyzed cross-labeling where binding partners become biotinylated, we have studied molecular interactions with an N-terminally fused GGH-tag proinsulin C-peptide. Since C-peptide has been reported to influence phosphatase activity in intact cells, we employed this method to study possible binding of the peptide to protein tyrosine phosphatase 1B (PTP-1B). C-peptide was found to interact with PTP-1B (and for control, also with antibodies to C-peptide), as did also the N- and C-terminal fragments of C-peptide which have sequence similarities with PTP-1B binding proteins. The labeling data combined with enzyme activity analysis indicate a functional interaction between acidic regions of C-peptide and specific sites of PTP-1B. Results highlight the importance of possible phosphatase/C-peptide roles in diabetes, and the usefulness of the cross-labeling reaction also for acidic peptides like C-peptide. |
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Keywords: | C-peptide Oxidative cross-labeling Phosphatase Protein interaction Affinity purification Metal binding Mass spectrometry |
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