Structure-function studies reveal ComEA contains an oligomerization domain essential for
transformation in gram-positive bacteria
Challenge
The core challenge addressed is
understanding how bacterial transformation works, particularly focusing on the process of
DNA uptake into the periplasm of Gram-positive and Gram-negative bacteria. A central player
in this process is ComEA, a DNA-binding protein essential for this uptake step. There are
differences in the structures of ComEA in Gram-positive versus Gram-negative bacteria that
are not yet understood, particularly a domain found in Gram-positive bacteria that drives
ComEA oligomerization.
Solution
X-ray crystal structures of ComEA from two Gram-positive
species, Bacillus subtilis and Geobacillus stearothermophilus, were determined. These
structures revealed a domain absent in Gram-negative bacteria, which drives ComEA
oligomerization.
Various analyses like X-ray crystallography, genetic,
and analytical ultracentrifugation (AUC) were employed to investigate this domain's role.
Multi-wavelength AUC was used to study the interaction
between DNA and the ComEA DNA-binding domain.
A model was proposed based on the collected
data. The model suggests that the oligomerization of ComEA provides a pulling force,
enabling DNA uptake across the thick cell walls of Gram-positive bacteria.
Conclusion
The research has revealed new structural and functional insights into ComEA, a protein
central to bacterial transformation. The identified oligomerization domain in ComEA,
specific to Gram-positive bacteria, is crucial for DNA uptake across their thick cell walls.
This discovery advances our understanding of bacterial transformation and highlights the
distinct molecular mechanisms employed by Gram-positive bacteria during this process.
