title: Studies on the subcellular localization of the membrane-bound fraction of intestinal calcium-binding protein.
abstract: Sorbitol density gradient centrifugation applied to intestinal mucosa homogenates resulted in a complete separation of soluble calcium-binding protein from the bound fraction of calcium-binding protein, providing further documentation of the bound pool of calcium-binding protein. The peak of the bound calcium-binding protein was not associated with the major peaks of any of the markers used, but was associated with minor peaks of alkaline phosphatase, RNA, and glucose-6-phosphatase. Lack of association of bound calcium-binding protein with (Na+ + K+)-ATPase indicated that the bound calcium-binding protein is not on the basolateral membrane. Differential centrifugation fractionation indicated that the bound calcium-binding protein is not associated with nuclei or mitochondria. The bound calcium-binding protein also could not be detected in partially purified brush borders. Exclusion of the brush border and basolateral membranes as the location of the bound calcium-binding protein suggests an intracellular locale.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000032:analysis*; D002499:Centrifugation, Density Gradient; D002645:Chickens; D005779:Immunodiffusion; D007413:Intestinal Mucosa / Q000032:analysis* / Q000648:ultrastructure; D008871:Microvilli / Q000032:analysis / Q000201:enzymology; D012279:Rickets / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D014807:Vitamin D / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D064030:S100 Calcium Binding Protein G; D014807:Vitamin D; D000469:Alkaline Phosphatase