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Ulrika Berg, Peter Bang, Christine Carlsson-Skwirut

Calpain proteolysis of insulin-like growth factor binding protein (IGFBP) -2 and -3, but not of IGFBP-1

Keywords: biosensor analysis, Ca2+ - activation, cleavage site, fragmentation, Kinetics, protease

Calpains are cytoplasmic Ca²⁺-regulated cysteine proteases that may regulate insulin-like growth factor (IGF)-independent actions of insulin-like growth factor binding proteins (IGFBPs) through IGFBP proteolysis. In this study, [¹²⁵I]-labeled IGFBP-2 and -3, but not IGFBP-1, were proteolyzed by Ca²⁺-activated m-calpain in vitro. Degradation of higher concentrations of the recombinant proteins IGFBP-2 and -3 by m-calpain was dose-dependent but was terminated within 20 minutes by autolysis. By subjecting proteolytic fragments to N-terminal amino acid sequence analysis, the primary cleavage sites in IGFBP-2 and -3 were localized to the non-conserved central linker regions. Using the biosensor technique, in vitro binding of m-calpain to IGFBP-3 was demonstrated to be a Ca²⁺-dependent reaction with a rapid on/off-rate.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 2007
Pages: -

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