# A histidine pseudokinase modulates polar growth and cell shape in Streptomyces venezuelae

## TL;DR

A pseudokinase protein called PsmA interacts with DivIVA to regulate polar growth and cell shape in Streptomyces bacteria.

## Contribution

The discovery of PsmA, a conserved pseudokinase that modulates the polarisome in Streptomyces.

## Key findings

- PsmA interacts and co-localizes with DivIVA at hyphal tips.
- Deletion of PsmA leads to aberrant cell shape and hyperbranching.
- PsmA modulates the dynamics of the DivIVA-based polar organelle.

## Abstract

Polar growth and cell shape determination in mycelium-forming Streptomyces bacteria depends on the function of a polarly localised multiprotein complex that directs cell wall synthesis – the polarisome. This complex assembles around the essential cell polarity determinant DivIVA, alongside other largely unknown components. We report here the discovery of a conserved hybrid histidine kinase-like protein, PsmA, that interacts and co-localises with DivIVA at the hyphal tips. Deletion of psmA affects the shape and dynamics of the polarisome, leading to aberrant cell shape and hyphal hyperbranching. PsmA is a pseudokinase that lacks the critical histidine residue in its catalytic core. Our results suggest that PsmA tunes the dynamics and properties of the DivIVA-based polar organelle in streptomycetes in parallel to but not redundantly with Scy and FilP, two coiled-coil proteins known to influence polarisome properties. In summary, PsmA interacts with DivIVA and modulates the integrity of the growth zones at hyphal tips.

A pseudokinase version of a hybrid histidine kinase is identified as part of the protein assembly that directs polar growth in Streptomyces bacteria. This protein, PsmA, interacts with the essential DivIVA and modulates polar growth and cell shape.