PCSK9, a member of the peptidase S8 family, reveals three major components in the pre-processed protein: the signal peptide; the N-terminal prodomain; the catalytic domain; and the C-terminal domain, which is further divided into three modules.
The solved structure of PCSK9 reveals four major components in the pre-processed protein: the signal peptide (residues 1-30); the N-terminal prodomain (residues 31-152); the catalytic domain (residues 153-425); and the C-terminal domain (residues 426-692), which is further divided into three modules. 
