Fig. 2: Structure and activity of the PI3KC2α kinase core domain.
From: Structural basis of phosphatidylinositol 3-kinase C2α function
a, Overall structure of PI3KC2αcore. Note that in this conformation, the short helix within the activation loop is disordered and only the N-terminal part of kα12 is folded. b, The kinase core domain (KD) of PI3KC2α in complex with ATP and Mg2+. P-loop (red), catalytic loop (orange) and activation loop (yellow) are well defined. ATP is found at the interface between the N and C lobes of the KD. c, Close-up view of the ATP-binding pocket. Green dashed lines indicate interactions. The Mg2+ ion (gray sphere) neutralizes the charges of D1146 and D1268 to enable phosphate binding of ATP (shown as sticks). R1251 in the catalytic loop interacts with the activation loop. Intramolecular interactions of D1250, H1252 and N1255 in the catalytic loop are identified. d, Model for diC4-PI(4)P binding to the KD of PI3KC2α. Surface representation of the KD with K1283 and R1284 in the activation loop contacting the 4-phosphate of PI(4)P. e, In vitro kinase activity of PI3KC2αΔN using either PI(4)P or PI as a substrate. Data represent mean ± s.d. from n = 3 experiments, one sample, two-tailed t-test with hypothetical mean of 100, ∗∗∗P = 0.0003. f, PI(3,4)P2-synthesizing activity of PI3KC2αΔN activation loop mutants. Mutation of K1283A and K1284A abrogates kinase activity. Data represent mean ± s.d. from n = 3 experiments, One sample, two-tailed t-test with hypothetical mean of 100, ∗P = 0.0263 and ∗∗∗∗P < 0.0001.
