signal 1 27 27 Potential.
Residues 1-27 are the signal peptide or pre-peptide. After that sits the
pro-peptide from 28-249. You will almost always find the pre-peptide before
(N-terminal) the pro-peptide. I am not aware of more than a handful proteins
with another pre-pro-peptide organisation.
See the wiki-entry for prepeptide that also hols the explanation of
pro-peptide:
The terms pre- and pro- in conjunction with -peptide are regularly mixed up in
the internet. The most common definition is that the pre-peptide holds the
signal that tells the cell where the protein should be. For example, a
pre-peptide can be the signal that tells the cell that this protein must go to
the outer membrane. A pro-peptide tends to hold the molecule inactive. Once
the pro-peptide is cleaved off, the protein becomes active. Extracellular
proteases, for example, often have a pro-peptide that gets cleaved once the
molecule is outside the cell. Take the Bacillolysin precursor as an example.
In its keywords in its SwissProt file (NPRE_BACCE; ac=P05806) we find:
propep 28 249 222 Activation peptide.
chain 250 566 317 Bacillolysin.