[Adenylate kinase and GDP-kinase activity of rod outer segments in the frog retina. Possible functional role of the T beta subunit of transducin].
Pure frog retina rod outer segments (ROS) preparations (A280/A500 = 2,1-2,3) catalyze the synthesis of ATP from ADP in the presence of Mg2+. Adenylate kinase (AK) (ATP:AMP phosphotransferase, EC 2.7.4.3) specific activities for ROS preparations are within the range 2-4 mumole per hour for mg protein. The enzymatic activity of investigated preparations is due to intact, but not destroyed ROS. The component which possesses AK is found in water-soluble, but not in membranous ROS fractions and seems to be a part of the predominant ROS plasma protein--GTP-binding complex of transducin. It has been shown, that this component is the T beta subunit of transducin and its enzymatic activity is controlled by other subunits of the transducin complex. The obtained results indicate that GDP kinase (ATP:GDP phosphotransferase, EC 2.7.4.6) activity of transducin depends on the work of both of T beta and T alpha subunits. It has been shown that in the ROS preparations synthesis of the ATP from ADP and GDP phosphorylation are stimulated by a lowering of Ca2+ concentration (less than 10(-5)-10(-7) M). T beta component is suggested to play the role of phosphotransferase which phosphorylates GDP associated with the T alpha subunits and it leads to formation of a complex T alpha X GTP which is an activator of vertebrate retina ROS phosphodiesterase.
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000263:Adenylate Kinase / Q000378:metabolism*; D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006153:Guanosine Diphosphate / Q000378:metabolism; D007525:Isoelectric Focusing; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000201:enzymology*; D011896:Rana temporaria; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D015293:Transducin
D008565:Membrane Proteins; D006153:Guanosine Diphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D000263:Adenylate Kinase; D009701:Nucleoside-Diphosphate Kinase; D015293:Transducin
Adenilatkinaznaia i GDP-kinaznaia aktivnost' preparatov naruzhnykh segmentov palochek setchatki liagushki. Vozmozhnaia funktsional'naia rol' sub''edinitsy T beta transdutsina.