Turkey erythrocytes possess a membrane-associated inositol 1,4,5-trisphosphate 3-kinase that is activated by Ca2+ in the presence of calmodulin.
Turkey erythrocytes contain soluble and particulate kinase activities which catalyse the ATP-dependent phosphorylation of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. The particle-bound activity accounts for approximately one-quarter of the total cellular Ins(1,4,5)P3 kinase, when assayed at a [Ca2+] of 10 nM. The particle-bound Ins(1,4,5)P3 kinase is not washed from the membrane by 0.6 M-KCl, yet may be solubilized by a variety of detergents. This suggests that it is an intrinsic membrane protein. The product of the membrane-bound Ins(1,4,5)P3 kinase is inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4], identifying the enzyme as an Ins(1,4,5)P3 3-kinase. In the presence of calmodulin, the membrane-associated Ins(1,4,5)P3 3-kinase is activated as [Ca2+] is increased over the range 0.2-1.0 microM. Under these conditions, the rates of dephosphorylation of Ins(1,3,4,5)P4 and Ins(1,4,5)P3 by phosphatases in the membrane fraction are unchanged.
Morris
A J
AJ
Department of Biochemistry, University of Birmingham, U.K.
Downes
C P
CP
Harden
T K
TK
Michell
R H
RH
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000201:enzymology*; D066298:In Vitro Techniques; D010770:Phosphotransferases / Q000097:blood*; D017853:Phosphotransferases (Alcohol Group Acceptor); D014422:Turkeys
D002147:Calmodulin; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D002118:Calcium