Evidence for a membrane-bound fraction of chick intestinal calcium-binding protein.
After homogenization of intestinal mucosa from vitamin D-replete chicks and high speed centrifugation, the major proportion of the vitamin D-induced calcium-binding protein is present in the supernatant fraction. However, the centrifugate, after repeated washing, contains significant amounts of bound calcium-binding protein that can be solubilized by Triton X-100. The bound calcium-binding protein is identical to soluble calcium-binding protein by the criteria of immunological identity, electrophoretic mobility, and molecular size, as determined by gel filtration chromatography. The bound calcium-binding protein is only partially released by sonication, osmotic shock or by ribonuclease treatment. Bound and soluble calcium-binding protein are not present in rachitic chick intestine. The addition of calcium-binding protein to rachitic mucosa prior to homogenization does not yield a Triton X-100 solubilizable form, indicating that bound calcium-binding protein in vitamin D-replete intestine is not due to adsorption or vesicular entrapment of soluble calcium-binding protein. The overall evidence suggests that part of the intestinal calcium-binding protein is membrane-bound.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002645:Chickens; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008970:Molecular Weight; D011092:Polyethylene Glycols; D011498:Protein Precursors / Q000378:metabolism
D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D011092:Polyethylene Glycols; D002118:Calcium