If we take a look at Ali’s info-laden phylogenetic tree of bacterial DACs (so much detail in here, dive in!) we find that the PanS family enzymes cluster separately from the rest of the tree and that there really is a strong division between the immune and the non-immune associated DACs.

So here is our final model for how we see PanDA defense operating: PanS makes c-di-AMP to keep PanE 'off'. Phage infection with Acb4 production leads to a decrease in free c-di-AMP, leading to activation of PanE. PanE disrupts the membrane.

PanDA is most defensive against phage harboring sponges in their genome. Selecting for escapers of defense identified mutations within the acb4 sponge implying this immune evasion gene is responsible for triggering PanDA. Acb4 knockout Bas69 and N4 phage are no longer defended against by PanDA.

Unlike cyclases in those other systems, PanS constitutively produces c-di-AMP in the absence of any stimuli- it does not sense phage infection directly. PanE, it turns out, is a toxic effector which drives membrane disruption but only in the absence of second messenger!

The c-di-AMP generated by PanS binds to a paired effector protein PanE, a membrane protein with a soluble 2TM-β-barrel receptor domain. This two gene architecture (synthase and effector) is very reminiscent of type I CBASS…but that’s not the whole story.

PanDA defense requires a synthase we call PanS that generates c-di-AMP (and some c-UMP-AMP?!). Surprisingly, PanS does this using a minimal version of a DAC protein fold with no appended regulatory or apparent sensor domains.

Diadenylate cyclases (DACs) have well characterized roles in bacterial physiology controlling a variety of important cell processes through their ability to produce the second messenger c-di-AMP. But we’d humbly like to add a new function of these enzymes to the list- antiphage immunity!

If we take a look at Ali’s info-laden phylogenetic tree of bacterial DACs (so much detail in here, dive in!) we find that the PanS family enzymes cluster separately from the rest of the tree and that there really is a strong division between the immune and the non-immune associated DACs.

So here is our final model for how we see PanDA defense operating: PanS makes c-di-AMP to keep PanE 'off'. Phage infection with Acb4 production leads to a decrease in free c-di-AMP, leading to activation of PanE. PanE disrupts the membrane.

PanDA is most defensive against phage harboring sponges in their genome. Selecting for escapers of defense identified mutations within the acb4 sponge, implying this immune evasion gene is responsible for triggering PanDA. Acb4 knockout Bas69 and N4 phage are no longer defended against by PanDA.

Unlike cyclases in CBASS and other defense systems, PanS constitutively produces c-di-AMP in the absence of any stimuli- it does not sense phage infection directly. PanE, it turns out, is a toxic effector which drives membrane disruption but only in the absence of second messenger!

The c-di-AMP generated by PanS binds to a paired effector protein PanE, a membrane protein with a soluble 2TM-β-barrel receptor domain. This two gene architecture (synthase and effector) is very reminiscent of type I CBASS…but that’s not the whole story.

PanDA defense requires a synthase we call PanS that generates c-di-AMP (and some c-UMP-AMP?!). Surprisingly, PanS does this using a minimal version of a DAC protein fold with no appended regulatory or apparent sensor domains.

Diadenylate cyclases (DACs) have well characterized roles in bacterial physiology controlling a variety of important cell processes through their ability to produce the second messenger c-di-AMP. But we’d humbly like to add a new function of these enzymes to the list- antiphage immunity!

PanDA defense requires a synthase we call PanS that generates c-di-AMP (and some c-UMP-AMP?!). Surprisingly, PanS does this using a minimal version of a DAC protein fold with no appended regulatory or apparent sensor domains.

Today I was honored to receive the UC Irvine Chancellor's Award for Distinguished Fostering of Undergraduate Research- but it's really about them. I'm proud of the team we've built here over the last 2.5 years. So many excellent undergrads!!!