TY - JOUR
T1 - Carboxyl-terminal fragments of phospholipase C-β1 with intrinsic G(q) GTPase-activating protein (GAP) activity
AU - Paulssen, Ruth H.
AU - Woodson, Jimmy
AU - Liu, Zheng
AU - Ross, Elliott M.
PY - 1996
Y1 - 1996
N2 - Fragments of the ~50 kDa COOH-terminal region of phospholipase C-β1 (PLC-β11), ranging in size from 14 to 38 kDa, were expressed in Escherichia coli, purified, and tested for their regulatory activities. As expected, none of the fragments had phospholipase activity. Several fragments, referred to as PLC tails, displayed GTPase-activating protein (GAP) activity for G(q), the G protein class that stimulates the PLC-βs in response to receptors. G(q) GAP activity is characteristic of intact PLC-βs. In reconstituted phospholipid vesicles that contained purified G(q) and ml muscarinic cholinergic receptors, the most active tails increased agonist-stimulated, steady-state GTPase activity over 4-fold. Stimulation of steady-state GTPase by the tails depended on receptors for facilitation of GDP-GTP exchange, suggesting that the tails act by accelerating hydrolysis of bound GTP. In addition to intrinsic GAP activity, one tail with high GAP activity and others with low or minimal activity potentiated the GAP activity of intact PLC-β1. Other tails inhibited PLC-β1s GAP effect. Both intrinsic GAP activity and potentiation of the PLC-β1 GAP effect were often biphasic, with maxima as low as 100 nM tail and declining activities at higher concentrations. Several tails inhibited either the phospholipase activity of PLC-β1, its stimulation by G(q), or both. The tails thus define the region of PLC-β1 that has G(q) GAP activity and suggest a mechanism of action in which the COOH terminus of PLC-βs can interact with G(q) and with other PLC- β1 molecules.
AB - Fragments of the ~50 kDa COOH-terminal region of phospholipase C-β1 (PLC-β11), ranging in size from 14 to 38 kDa, were expressed in Escherichia coli, purified, and tested for their regulatory activities. As expected, none of the fragments had phospholipase activity. Several fragments, referred to as PLC tails, displayed GTPase-activating protein (GAP) activity for G(q), the G protein class that stimulates the PLC-βs in response to receptors. G(q) GAP activity is characteristic of intact PLC-βs. In reconstituted phospholipid vesicles that contained purified G(q) and ml muscarinic cholinergic receptors, the most active tails increased agonist-stimulated, steady-state GTPase activity over 4-fold. Stimulation of steady-state GTPase by the tails depended on receptors for facilitation of GDP-GTP exchange, suggesting that the tails act by accelerating hydrolysis of bound GTP. In addition to intrinsic GAP activity, one tail with high GAP activity and others with low or minimal activity potentiated the GAP activity of intact PLC-β1. Other tails inhibited PLC-β1s GAP effect. Both intrinsic GAP activity and potentiation of the PLC-β1 GAP effect were often biphasic, with maxima as low as 100 nM tail and declining activities at higher concentrations. Several tails inhibited either the phospholipase activity of PLC-β1, its stimulation by G(q), or both. The tails thus define the region of PLC-β1 that has G(q) GAP activity and suggest a mechanism of action in which the COOH terminus of PLC-βs can interact with G(q) and with other PLC- β1 molecules.
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U2 - 10.1074/jbc.271.43.26622
DO - 10.1074/jbc.271.43.26622
M3 - Article
C2 - 8900136
AN - SCOPUS:0029864554
SN - 0021-9258
VL - 271
SP - 26622
EP - 26629
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 43
ER -