XXXX -binding protein in small intestine. Identification, isolation, and evidence for its role in cellular @entity844 transport.

@entity21991 @entity844 @entity1718 @entity35
A soluble @entity844 -binding protein ( @entity21991 ), mol wt approximately 12,000 is present in intestinal mucosa and other tissues that utilize @entity1718 , including liver, myocardium, adipose, and kidney. This protein binds long chain @entity1718 both in vivo and in vitro. @entity21991 was isolated from @entity35 intestine by gel filtration and isoelectric focusing. It showed a reaction of complete immunochemical identity with proteins in the 12,000 mol wt @entity844 -binding fractions of liver, myocardium, and adipose tissue supernates. (The presence of immunochemically nonidentical 12,000 mol wt @entity21991 in these tissues is not excluded.) By quantitative radial immunodiffusion, supernatant @entity21991 concentration in mucosa from proximal and middle thirds of jejuno-ileum significantly exceeded that in distal third, duodenum, and liver, expressed as micrograms per milligram soluble protein, micrograms per gram DNA, and micrograms per gram tissue. @entity21991 concentration in villi was approximately three times greater than in crypts. Small quantities of @entity21991 were present in washed nuclei-cell membrane, mitochondrial and microsomal fractions. However, the amount of @entity21991 solubilized per milligram membrane protein was similar for all particulate fractions, and total membrane-associated @entity21991 was only about 16% of supernatant @entity21991 . Intestinal @entity21991 concentration was significantly greater in animals maintained on high fat diets than on low fat; saturated and unsaturated fat diets did not differ greatly in this regard.The preponderance of @entity21991 in villi from proximal and middle intestine, its ability to bind @entity1718 in vivo as well as in vitro, and its response to changes in dietary fat intake support the concept that this protein participates in cellular @entity844 transport during fat absorption. Identical or closely related 12,000 mol wt proteins may serve similar functions in other tissues.
