Faculty Collaboration Database

Purification of calciferol-binding proteins from kidney: physicochemical and immunological properties. J Lipid Res 1978 Jul;19(5):601-12

Date

07/01/1978

Pubmed ID

670835

Scopus ID

2-s2.0-0018140512 (requires institutional sign-in at Scopus site)   8 Citations

Abstract

The calciferol-binding system of rat kidney cytosol has been purified and is shown to consist of two proteins, each capable of binding either 25-hydroxy-vitamin D3 (25-OH-D3) or 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). The two proteins, designated A and B, have similar sedimentation coefficients (S20w) of 5.2 S. Component A binds 25-OH-D3 with a dissociation constant (Kd) of 10(-7) M while component B binds 1,25-(OH)2D3 with a Kd of 1.6 x 10(-8) M. The estimated molecular weights (Mr) of the two proteins are 105,000 for component A and 250,000 for component B. Amino acid analyses revealed that glutamic acid is the most abundant residue in both proteins, comprising 12% of the total number of amino acid residues. Immunodiffusion test using commercial anti-human serum group-specific protein antiserum gave a precipitin reaction when purified rat serum calciferol-binding protein was used as an antigen, but no reactions could be detected with proteins A and B. This result significantly eliminated the possibility of the presence of the rat serum binding protein in either of the purified kidney proteins. In contrast, anti-rat serum calciferol-binding protein antiserum prepared in rabbits interacted with the rat serum and kidney proteins. This result suggests that the antigenic determinants recognized by the antiserum against the rat serum calciferol-binding protein appear to be similar to those recognized in the kidney proteins A and B. Immunoelectrophoresis of the three rat proteins demonstrated dissimilar electrophoretic mobilities with the serum protein showing the least mobility, a property consistent with its higher lysine content relative to proteins A and B.

Author List

Ghazarian JG, Hsu PY, Girotti AW, Winkelhake JL

Author

Albert W. Girotti PhD Adjunct Professor in the Biochemistry department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acids
Animals
Binding, Competitive
Carrier Proteins
Dihydroxycholecalciferols
Hydroxycholecalciferols
Immunoelectrophoresis
Kidney
Molecular Weight
Rats
Ultracentrifugation