Abstract A method of purification of a vitamin D-dependent calcium-binding protein from chick intestinal mucosa is described. The purification procedure involved the use of ammonium sulfate precipitation, gel filtration on Sephadex G-100, and preparative disc electrophoresis. The assay system for calcium-binding protein is based upon the competition between calcium-binding protein and an ion exchange resin for added 45Ca. An equation linearly relating binding protein concentration to binding activity is given. Sedimentation velocity and gel filtration behavior indicated that the product was homogeneous with respect to size. Two acrylamide gel systems gave single bands, whereas a third showed the presence of a possible degradation product in addition to calcium-binding protein. The molecular weight of calcium-binding protein was found to be about 2.8 x 104 by calibrated gel filtration and about 2.5 x 104 by equilibrium sedimentation (assumed partial specific volume = 0.72). The formation constants between calcium-binding protein and calcium, strontium, and barium were 2.6 x 105 m-1, 3.9 x 104 m-1, and 5.8 x 103 m-1, respectively, and it appears that 1 mole of protein binds 1 atom of calcium. Preliminary analysis of the composition of the protein is reported.
ABSTRACT
PUBLICATION RECORD
- Publication year
1968
- Venue
Journal of Biological Chemistry
- Publication date
1968-07-25
- Fields of study
Biology, Medicine, Chemistry
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
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