Function 
Rhomboid protease (GlpG) is a transmembranal serine protease.  The active site is buried in the lipid bilayer of cell membrane.  It cleaves proteins within their transmembrane domain[1].  Rhomboids regulate many cellular processes and are involved in many human diseases.  The catalytic site of rhomboids contains a hydrophilic pocket protected from the lipid bilayer.  Rhomboids are specific for a single transmembranal helix proteins.
  Structural highlights 
The inhibitor  (in deepskyblue)[2]. . Water molecules shown as red spheres.