Phosphorylcholine, a specific component of the teichoic acids of the pneumococcal cell wall, plays a key role in the mechanisms of pneumococcal infection to humans through direct binding to the receptor of platelet-activating factor (PAF), as well as a anchor for an entire family of pneumococcal surface proteins (the choline-binding protein, CBP). The structure of phosphorylcholine esterase (Pce), the first described for a complete pneumococcal CBP, has been resolved by X-ray diffraction by a team of scientists from the National Research Council, led by John A.

Beautiful. The Pce, 57 kDa, presents a novel modular structure with a globular catalytic module responsible for the hydrolysis of phosphorylcholine into teichoic acid, and choline-binding module very long (more than 100 ìm), which allows anchor to the wall of pneumococcus. The structure has allowed to describe the catalytic mechanism which has a central role binuclear zinc, and understanding how this enzyme in vivo. The union of the two modules, which are structurally very different, is carried out by the presence of a long loop stabilized by calcium ions.

The finding by the team that hydrolyzes Pce factor activation of platelets, important cellular messenger that is activated in inflammatory processes and the role that has Pce removing phosphorylcholine molecules present on the outer surface pneumococcus, avoiding the recognition and elimination by the human immune system components, provide new avenues in understanding the molecular mechanisms of pneumococcal infection and invasion.