The P 1 position refers to {TAIL ~ the amino acid} which precedes {HEAD ~ the amino acid residue} of the peptide that occupies the P1 pocket 
The P 1 position refers to { TAIL ~ the amino acid } which precedes { HEAD ~ the amino acid residue } of the peptide that occupies the P1 pocket
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH