Purification of the major GTP-binding proteins from human placental membranes.

摘要: Using minor modifications of procedures developed to purify GTP-binding proteins (G-proteins) from rabbit liver, we have purified the major G-proteins present in human placental membranes. One, referred as Gi, is substrate for pertussis toxin-catalyzed ADP-ribosylation and has an alpha-subunit 41,000 daltons, beta-subunit 36,000 35,000 a gamma-subunit 10,000 daltons. The other protein, Gp, was identified by its ability bind guanine nucleotides specifically with high affinity. This activity resolved Gs Gi second step purification (AcA-34 chromatography) further through heptylamine-Sepharose hydroxylapatite. nucleotide-binding site, which can be performance liquid chromatography photolyzable GTP analogue, associated 21,000-dalton protein (Gp alpha) that copurifies beta gamma-subunits indistinguishable Gi. represents potentially novel member structurally functionally homologous family are transducing elements receptor-mediated regulation variety cellular processes.