Purification and characterization of ouabain-binding protein in human plasma.
Ouabainlike factors are thought to be a kind of important modulators of salt and water metabolism in essential hypertension. We purified the binding-protein of ouabain (OBP) from human plasma. The amino-terminal sequence of OBP from human plasma, (NH2-TLGQPREPQVYTLPPXREEM-), indicated that OBP is the carboxy-terminal fragment (14.4 kDa by SDS-PAGE) from T218 of IgG2 heavy chain and from A221 of the IgG1 heavy chain constant region. Moreover, plasmin-cleaved Fc fragment (pFc) of IgG possessed the ouabain-binding activity by the gel-filtration method of pFc and authentic ouabain mixture, whereas neither intact, aggregate, nor papain-cleaved Fc fragment did. The amino-terminal sequence of pFc was NH2-THTXPPXPAPELLGGPXVFL-, and this sequence corresponded to the T105 to L125 fragment of the IgG1 heavy chain constant region. The growth of cultured THP-1 cells were arrested in the dose-dependent manner by ouabain, which was inhibited by the addition of 20 microg/mL of pFc. These results suggested that plasmin-cleaved Fc of human IgG is one of the binding protein of ouabain/ouabainlike factor(s) in human plasma.
Komiyama
Y
Y
Department of Clinical Sciences and Laboratory Medicine, Kansai Medical University, Moriguchi, Osaka, Japan.
Nishimura
N
N
Nishino
N
N
Okuda
K
K
Munakata
M
M
Kosaka
C
C
Masuda
M
M
Takahashi
H
H
D002455:Cell Division / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005341:Fibrinolysin / Q000494:pharmacology; D005343:Fibrinolytic Agents / Q000494:pharmacology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007938:Leukemia / Q000473:pathology; D010042:Ouabain / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood / Q000302:isolation & purification* / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004791:Enzyme Inhibitors; D005343:Fibrinolytic Agents; D007074:Immunoglobulin G; C028996:cardiac glycoside receptors; D010042:Ouabain; D005341:Fibrinolysin; D000254:Sodium-Potassium-Exchanging ATPase