Purification and characterization of the adenosine A2-like binding site from human placental membrane
We have purified and characterized the adenosine A2-like binding site from human placental membranes. 5'-N-Ethylcarboxamido[2,8-3H]adenosine ([3H]NECA) binds to this site, with a Kd of 240 nM and a Bmax of 13.0 pmol/mg in human placental membranes. The adenosine A2-like binding site was purifie...
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Veröffentlicht in: | The Journal of biological chemistry 1989-11, Vol.264 (33), p.19898-19903 |
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Sprache: | eng |
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Zusammenfassung: | We have purified and characterized the adenosine A2-like binding site from human placental membranes. 5'-N-Ethylcarboxamido[2,8-3H]adenosine
([3H]NECA) binds to this site, with a Kd of 240 nM and a Bmax of 13.0 pmol/mg in human placental membranes. The adenosine
A2-like binding site was purified after extraction from placental membranes with 0.1% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic
acid. The purification included ammonium sulfate precipitation and concanavalin A, DEAE-Sephadex, and Sepharose 6B gel filtration
chromatographies. The protein was purified 127-fold to homogeneity, with a final specific activity of 1.5-1.9 nmol/mg of protein
and a 5.5-8.1% yield of binding activity from the membranes. The purified protein had similar binding properties and an identical
potency order for displacement of [3H] NECA by adenosine analogs as the initial membranes. Sodium dodecyl sulfate-polyacrylamide
gel electrophoresis of purified protein revealed a single band at 98 kDa which coeluted with [3H]NECA binding activity during
Sepharose 6B gel filtration chromatography. In 0.1% Triton X-100, the binding complex has a Stokes radius of 70 A, a sedimentation
coefficient of 6.9 S, and a partial specific volume of 0.698 ml/g. The detergent-protein complex has a calculated molecular
mass of 230 kDa. The estimated frictional ratio is 1.5. The native binding complex appears to consist of a dimer of identical
subunits. The function of this ubiquitous protein remains unclear. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(19)47195-0 |