Iments: LPR MB DLJ. Performed the experiments: LPR MB DT. Analyzed the data: LPR MB DLJ. Contributed reagents/materials/analysis tools: TF. Wrote the paper: LPR LJ.
PKCa (protein kinase C a) is a classical PKC 1317923 isoenzyme that is activated by second messengers, namely the increase in Ca2+ concentration in the cytoplasm of the cell and the appearance of diacylglycerol in the membrane, where it establishes specific interactions with phosphatidylserine and PIP2 [1]. The translocation of classical PKCs (cPKCs) to the plasma membrane is mediated by the C1 and C2 domains, and it has been shown that initial membrane affinity is mainly determined by C2 domain embrane interactions, followed by C1 domain iacylglycerol interactions [1]. One of the main sources of diacylglycerol in the plasma membrane following cell stimulation is PIP2 11967625 which is hydrolyzed by phospholipase C to produce diacylglycerol and inositol 1,4,5-trisphosphate, which together activate protein kinase C for sustained cellular responses [2]. However, it has been shown that PIP2 may also activate PKCa by direct binding to a polylysine motif located in Title Loaded From File strands b3 and b4 [3?] and that can be considered a specific site for PIP2 [8] (see Fig. 1). Other molecules like phosphatidylserine or phosphatidic acid [9] or even retinoic acid [10] may also bind with lower affinity to this site. It has been clearly shown that PIP2 is important for PKCa translocation to themembrane and for prolonging this translocation. Rapid [5,11,12] kinetics studies on the binding of this enzyme to model membranes suggested that the interaction of PKCa with membranes occurs via two steps: a rapid weak recruitment to the membrane due to non-specific interactions with (primarily) anionic lipids and the formation of a high affinity complex due to stereospecific interactions of each PKCa domain with its specific ligands [12]. PKCa enzyme is a paradigmatic example for bearing a C2 domain which may simultaneously bind three different activators, in this case Ca2+, phosphatidylserine and PIP2. Fig. 1 shows this C2 domain in which Ca2+ binds to its site, acting as a bridge for phosphatidylserine, although this phospholipid also directly interacts with several protein residues [13,14]. In another site located in a b-groove, PIP2 binds with great affinity. Previous work has shown that PKCa exhibits high cooperativity in its activity by phosphatidylserine [15,16] and that the two second messengers of the kinase, diacylglycerol and Ca2+, markedly increase the affinity of the kinase for phosphatidylserine [17]. In this paper, we use highly purified full-length PKCa to perform a kinetic study of the activation of PKCa by model membranes, in which the concentrations of POPS, DOG, PIPPIP2 Activation of PKCaPMSF, 10 mg/ml leupeptin and 10 mM benzamidine. The pellet was disrupted by sonication (6610 s) and the resulting lysate was centrifuged at 15000 rpm for 20 min. The supernatant was applied to a 1 ml Title Loaded From File His-Gravi TrapTMH column (GE Healthcare, Barcelona, Spain) and equilibrated with 25 mM Tris-HCl pH 7.5, 150 mM NaCl and 20 mM imidazole buffer. The bound proteins were eluted by an imidazole gradient (20?00 mM). Fractions containing protein kinase Ca from a His-Gravi TrapTMH column were pooled, concentrated by ultrafiltration to a 2 mL volume and adjusted by the addition of 5 M NaCl to give a NaCl concentration of 1 M. This fraction was then processed by hydrophobic exchange chromatography, directly applying it to a SOURCE 15PHE 4.Iments: LPR MB DLJ. Performed the experiments: LPR MB DT. Analyzed the data: LPR MB DLJ. Contributed reagents/materials/analysis tools: TF. Wrote the paper: LPR LJ.
PKCa (protein kinase C a) is a classical PKC 1317923 isoenzyme that is activated by second messengers, namely the increase in Ca2+ concentration in the cytoplasm of the cell and the appearance of diacylglycerol in the membrane, where it establishes specific interactions with phosphatidylserine and PIP2 [1]. The translocation of classical PKCs (cPKCs) to the plasma membrane is mediated by the C1 and C2 domains, and it has been shown that initial membrane affinity is mainly determined by C2 domain embrane interactions, followed by C1 domain iacylglycerol interactions [1]. One of the main sources of diacylglycerol in the plasma membrane following cell stimulation is PIP2 11967625 which is hydrolyzed by phospholipase C to produce diacylglycerol and inositol 1,4,5-trisphosphate, which together activate protein kinase C for sustained cellular responses [2]. However, it has been shown that PIP2 may also activate PKCa by direct binding to a polylysine motif located in strands b3 and b4 [3?] and that can be considered a specific site for PIP2 [8] (see Fig. 1). Other molecules like phosphatidylserine or phosphatidic acid [9] or even retinoic acid [10] may also bind with lower affinity to this site. It has been clearly shown that PIP2 is important for PKCa translocation to themembrane and for prolonging this translocation. Rapid [5,11,12] kinetics studies on the binding of this enzyme to model membranes suggested that the interaction of PKCa with membranes occurs via two steps: a rapid weak recruitment to the membrane due to non-specific interactions with (primarily) anionic lipids and the formation of a high affinity complex due to stereospecific interactions of each PKCa domain with its specific ligands [12]. PKCa enzyme is a paradigmatic example for bearing a C2 domain which may simultaneously bind three different activators, in this case Ca2+, phosphatidylserine and PIP2. Fig. 1 shows this C2 domain in which Ca2+ binds to its site, acting as a bridge for phosphatidylserine, although this phospholipid also directly interacts with several protein residues [13,14]. In another site located in a b-groove, PIP2 binds with great affinity. Previous work has shown that PKCa exhibits high cooperativity in its activity by phosphatidylserine [15,16] and that the two second messengers of the kinase, diacylglycerol and Ca2+, markedly increase the affinity of the kinase for phosphatidylserine [17]. In this paper, we use highly purified full-length PKCa to perform a kinetic study of the activation of PKCa by model membranes, in which the concentrations of POPS, DOG, PIPPIP2 Activation of PKCaPMSF, 10 mg/ml leupeptin and 10 mM benzamidine. The pellet was disrupted by sonication (6610 s) and the resulting lysate was centrifuged at 15000 rpm for 20 min. The supernatant was applied to a 1 ml His-Gravi TrapTMH column (GE Healthcare, Barcelona, Spain) and equilibrated with 25 mM Tris-HCl pH 7.5, 150 mM NaCl and 20 mM imidazole buffer. The bound proteins were eluted by an imidazole gradient (20?00 mM). Fractions containing protein kinase Ca from a His-Gravi TrapTMH column were pooled, concentrated by ultrafiltration to a 2 mL volume and adjusted by the addition of 5 M NaCl to give a NaCl concentration of 1 M. This fraction was then processed by hydrophobic exchange chromatography, directly applying it to a SOURCE 15PHE 4.
