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