Amino Acid Sequence of pi 5 from Avian Myeloblastosis Virus Complex

The complete amino acid sequence of the pi 5 gag protein from avian myeloblastosis virus (AMV) complex has been determined by sequential Edman degradation of the intact molecule and of peptide fragments generated by limited tryptic cleavage, cleavage with staphylococcal protease, and cyanogen bromide cleavage. AMV pi5 is a single-chain protein containing 124 amino acids. The charged amino acids tend to be clustered in the primary structure, pi5 contains a single cysteine at position 113 which may be essential for the pi5 associated proteolytic activity. However, pi 5 shows no appreciable sequence homology with papain or other classical thiol proteases.