A Kunitz-type proteinase inhibitor with differential solubility during the development of potato (Solanum tuberosum L.) tubers |
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| Authors: | Cristina Mitsumori K. Yamagishi T. Itoh Y. Kikuta |
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| Affiliation: | (1) Laboratory of Crop Physiology, Faculty of Agriculture, Hokkaido University, 060 Sapporo, Japan;(2) Laboratory of Electronic Microscopy. Faculty of Agriculture, Hokkaido University, 060 Sapporo, Japan;(3) Present address: Section of Plant Biology, Division of Biological Sciences, University of California, 95616 Davis, California, USA |
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| Abstract: | Summary Two potato (Solanum tuberosum L., cv. Irish Cobbler) Kunitz-type proteinase inhibitors (PKPI) were previously described to be present in the soluble fraction of proteins from tubers in the early stages of development. One of them became insoluble in mature tubers, being extractable from this material in presence of urea. Amino acid sequencing showed that the soluble and insoluble PKPI were identical to each other. Also, immunolocalization using the protein A-gold method showed that both proteins were present inside the vacuole in free (intravacuolar space) and aggregated forms. The density of PKPI in the vacuolar protein aggregates increased from developing to mature tubers. showing that the soluble-insoluble state of this protein is related to the aggregation levels. Purified PKPI precipitated in vitro. mainly in presence of high calcium concentrations and low pH, but this precipitated form was not as stable as aggregates found in vivo. Based on the results obtained, a model of PKPI insolubilization in vivo is discussed. |
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| Keywords: | immunocytology protein solubility |
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