Ye, F., Huang, Y., Li, J., Ma, Y., Xie, C., Liu, Z., Deng, X., Wan, J., Xue, T., Liu, W., and Zhang, M.(2018). eLife, 7, e41848.

INAD assembles key enzymes of the Drosophila compound eye photo-transduction pathway into a supramolecular complex, supporting efficient and fast light signaling. However, the molecular mechanism that governs the interaction between INAD and NORPA (phospholipase Cβ, PLCβ), a key step for the fast kinetics of the light signaling, is not known. Here, we show that the NORPA C-terminal coiled-coil domain and PDZ-binding motif (CC-PBM) synergistically bind to INAD PDZ45 tandem with an unexpected mode and unprecedented high affinity. Guided by the structure of the INAD–NORPA complex, we discover that INADL is probably a mammalian counterpart of INAD. The INADL PDZ89 tandem specifically binds to PLCβ4 with a mode that is strikingly similar to that of the INAD–NORPA complex, as revealed by the structure of the INADL PDZ89–PLCβ4 CC-PBM complex. Therefore, our study suggests that the highly specific PDZ tandem – PLCβ interactions are an evolutionarily conserved mechanism in PLCβ signaling in the animal kingdom.

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