filamentous phage display p3 filamentous phage display MI:0899 low valency display PSI-MI pIII is one of the minor coat proteins that decorates in five copies the emerging tip of filamentous phage. Similarly to pVIII pIII also tolerates peptide insertions at the amino-terminus. The sequences to be displayed can either be encoded in the phage copy of the coat gene or in an extra pIII gene copy carried on a phagemid. In the first case 5 copies o the hybrid proteins are displayed while in the latter only a few capsid display one copy and the majority display none. Because of the low copy number pIII display is often referred to as low valency display. p3 filamentous phage