The role of membrane-associated iron-binding complex in intestinal iron absorption in the rat.
A membrane-associated iron-binding complex was isolated from rat intestinal mucosa during iron absorption. Two 59Fe peaks (peaks 1 and 2) were separated on Sepharose 6B gel filtration from detergent solubilized 20,000 x g precipitate of upper intestinal mucosal homogenate after administration of 59Fe-labelled ferrous materials. Peak 1 was a membrane iron-binding complex whose apparent molecular weight was over 10(6) Da estimated by gel filtration, while peak 2 was identified as ferritin. Three major bands were detected on SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of peak 1. The treatment of mucosal homogenate with 5 mM ethylenediaminetetraacetic acid released 59Fe binding from peak 1. Incorporation of 59Fe to peak 1 showed the maximum at 1 h and then reduced, while [59Fe]ferritin showed reciprocal behavior, which suggested that peak 1 may be a rapid turnover iron pool and transfer 59Fe to ferritin. Peak 1 was also isolated from the brush border membrane and showed similar SDS-PAGE pattern to that from the 20,000 x g precipitate of mucosal homogenate. Western blot analysis did not reveal immunoreactive transferrin in peak 1. Those findings suggest that peak 1 may be a non-ferritin, non-transferrin iron-binding complex located on the brush border membrane and accept iron from the intestinal canal during iron absorption.
Orimo
H
H
Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan.
Hisayasu
S
S
Hirai
Y
Y
Yoshino
Y
Y
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D004492:Edetic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005293:Ferritins / Q000378:metabolism; D007408:Intestinal Absorption; D007501:Iron / Q000378:metabolism*; D007504:Iron Radioisotopes; D033862:Iron-Binding Proteins; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D051381:Rats; D017208:Rats, Wistar; D014168:Transferrin / Q000302:isolation & purification / Q000378:metabolism; D033863:Transferrin-Binding Proteins
D002352:Carrier Proteins; D007504:Iron Radioisotopes; D033862:Iron-Binding Proteins; D014168:Transferrin; D033863:Transferrin-Binding Proteins; D005293:Ferritins; D004492:Edetic Acid; D007501:Iron