Interaction of the low-molecular-mass, guanine-nucleotide-binding protein with the actin-binding protein and its modulation by the cAMP-dependent protein kinase in bovine platelets.
Platelets have been shown to possess several, different, low-molecular-mass, guanine-nucleotide-binding proteins (G-proteins) with molecular masses about 20-30 kDa. We report here that a 25-kDa G-protein copurified with the bovine platelet actin-binding protein (ABP), a cross-linker of actin filaments which is known to generate the three-dimensional network of actin. Both the G-protein and ABP were recovered in a fraction that was insoluble in Triton X-100 and were extracted in 0.6 M NaCl. Gel-filtration chromatography of the high-salt extract and rechromatography in a low-salt solution indicated that the two proteins may be associated with each other. The association of the two proteins was suggested by cosedimentation of the G-protein with the actin gel formed by actin and ABP. The amounts of the cosedimented G-protein and ABP was unaffected by guanosine-5'-O-[beta-thio]diphosphate and guanosine-5'-O-[gamma-thio]triphosphate, but the G-protein, not ABP, was partially released from the actin gel by phosphorylating ABP with cAMP-dependent protein kinase. Thus, the association of the two proteins was affected by modification of ABP, but not by modification of G-proteins. The physiological significance of the possible association of the two proteins might be that the membrane skeleton functions as a modulator of the G-protein, rather than that the G-protein modulates the function of the membrane skeleton which comprises ABP.
Ueda
M
M
Department of Biology, College of General Education, Osaka University, Toyonaka, Japan.
Oho
C
C
Takisawa
H
H
Ogihara
S
S
D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000378:metabolism; D001792:Blood Platelets / Q000201:enzymology*; D015153:Blotting, Western; D002417:Cattle; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D008970:Molecular Weight; D010766:Phosphorylation; D010777:Photochemistry; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism*; D013873:Thionucleotides / Q000378:metabolism
C021961:8-azidoguanosine triphosphate; D000345:Affinity Labels; D001386:Azides; D008840:Microfilament Proteins; D013873:Thionucleotides; D006153:Guanosine Diphosphate; C032829:6-thioguanosine 5'-diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D011494:Protein Kinases; D019204:GTP-Binding Proteins