Purification, characterization, and localization of 70 kDa calcium-sensitive protein (calelectrin) from mammary glands
✍ Scribed by Joseph J. Lozano; Alfred H. Haindl; Victor Rocha
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 804 KB
- Volume
- 141
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Mammary glands contain a group of calcium-sensitive proteins that bind to membranes in a calcium-dependent manner. Using the calcium-dependent binding to hydrophobic surfaces in combination with conventional techniques, we have purified the 70 kDa mammary calcium-binding protein (70 kDa M-CBP) to homogeneity. Antisera prepared to the 70 kDa M-CBP or to bovine liver 67 kDa calelectrin reacted in immunoblot analysis with the 70 kDa M-CBP antigen and with several additional mammary CBP species in crude tissue homogenates. Limited proteolysis of the 70 kDa M-CBP produced smaller immunoreactive species; extensive proteolysis resulted in more complete degradation of the protein. Identical data were obtained with digestion of 67 kDa calelectrin. The pl for the 70 kDa M-CBP was determined to be approximately 5.8; the same value reported for 67 kDa calelectrin. Phosphorylation of 70 kDa M-CBP was not detected in epithelial cell culture metabolic labeling. lmmunohistochemical localization showed the protein to be located in ductal epithelia of virgin mouse mammary glands with a pattern of increased staining of the basal portions of the cells. Some stromal cells were also reactive. Apparently, the 70 kDa M-CBP and 67 kDa calelectrin are the same protein. Furthermore, like the 32.5 calelectrin (endonexin) and calpactin l/p36/1ipocortin II, the 70 kDa protein appears to be a ductal epithelial cell associated protein in the mammary gland.