Lipoteichoic acid (LTA) is an important cell wall component
required for proper cell growth in many Gram-positive bacteria.
In Listeria monocytogenes, two enzymes are required for the synthesis
of this polyglycerolphosphate polymer. The LTA primase
LtaPLm initiates LTA synthesis by transferring the first glycerolphosphate
(GroP) subunit onto the glycolipid anchor and the
LTA synthase LtaSLm extends the polymer by the repeated addition
of GroP subunits to the tip of the growing chain. Here, we
present the crystal structures of the enzymatic domains of
LtaPLm and LtaSLm. Although the enzymes share the same fold,
substantial differences in the cavity of the catalytic site and
surface charge distribution contribute to enzyme specialization.
The eLtaSLm structure was also determined in complex
with GroP revealing a second GroP binding site. Mutational
analysis confirmed an essential function for this binding site
and allowed us to propose a model for the binding of the
growing chain.