Library and degenerate codon designs to generate Pdu signal sequences. (A) Multiple sequence alignment of PduP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, rational signal sequence design, library hits A.1 and B.1, Regan and DeGrado alpha helical design, and library hit DeGrado.1; (B) degenerate codons used to generate polar/charged or hydrophobic amino acids, and corresponding encoded amino acids; and (C) detailed library designs for Library A, Library B, and Library DeGrado. Degenerate codons are specified according to the Nomenclature for Incompletely Specified Bases in Nucleic Acid Sequences.