PMID: 22705373

Authors:

Yin Q, Tian Y, Kabaleeswaran V, Jiang X, Tu D, Eck MJ, Chen ZJ, Wu H

Title:

Cyclic di-GMP Sensing via the Innate Immune Signaling Protein STING.

Journal:

Mol Cell. 2012 Jun 29;46(6):735-45. Epub 2012 Jun 14.

Abstract:

Detection of foreign materials is the first step of successful immune responses. Stimulator of interferon genes (STING) was shown to directly bind cyclic diguanylate monophosphate (c-di-GMP), a bacterial second messenger, and to elicit strong interferon responses. Here we elucidate the structural features of the cytosolic c-di-GMP binding domain (CBD) of STING and its complex with c-di-GMP. The CBD exhibits an alpha + beta fold and is a dimer in the crystal and in solution. Surprisingly, one c-di-GMP molecule binds to the central crevice of a STING dimer, using a series of stacking and hydrogen bonding interactions. We show that STING is autoinhibited by an intramolecular interaction between the CBD and the C-terminal tail (CTT) and that c-di-GMP releases STING from this autoinhibition by displacing the CTT. The structures provide a remarkable example of pathogen-host interactions in which a unique microbial molecule directly engages the innate immune system.