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Isolation and characterization of plasma membranes from guinea pig ileum

Conference · · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
OSTI ID:5220117
A plasma membrane fraction from guinea pig ileum has been isolated by extraction of a crude microsomal fraction with a low ionic strength buffer containing ATP and Ca/sup 2 +/. The extracted microsomes were subjected to sucrose-density-gradient centrifugation in the presence of 0.6 M KCl. The plasma membranes were substantially free from contamination with contractile proteins, mitochondria and sarco-plasmic reticulum. The plasma membrane vesicles were enriched 30-to-40-fold in Na/sup +/-K/sup +/-ATPase and 5'-nucleotidase activities. The plasma membrane vesicles accumulated Ca/sup 2 +/ in the presence of ATP. The addition of Ca/sup 2 +/ ionophore A23187 to vesicles loaded with Ca/sup 2 +/ in the presence of ATP removed Ca/sup 2 +/ completely from the vesicles in one minute. The Km values for the Ca/sup 2 +/ -dependent phosphorylated intermediates of Ca/sup 2 +/ -Mg/sup 2 +/ -ATPase and Ca/sup 2 +/ uptake were approximately 0.8 ..mu..M indicating that the phosphorylated intermediates represent phosphorylation of Ca/sup 2 +/ pump ATPase. The /sup 3/H-nitrendipine binding to plasma membranes was characterized by high affinity with Kd of 185 pM and B/sub max/ 1280 fmol/mg protein. The plasma membrane vesicles prepared by these procedures can prove useful for the study of ion transport.
Research Organization:
Univ. of Iowa, Iowa City
OSTI ID:
5220117
Report Number(s):
CONF-8604222-
Conference Information:
Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:3
Country of Publication:
United States
Language:
English