Evolutional selection of a combinatorial phage library displaying randomly-rearranged various single domains of immunoglobulin (Ig)-binding proteins (IBPs) with four kinds of Ig molecules

Table 3 Sequences of random linking peptides in PA(A)-PL structure and their distribution in hIgM and hIgA selected libraries

Combinatorial form of single domains	PA(A)-PL-PL_9N	PA(A)_6N-PL_9N	PA(A)-PL_3N	PA(A)_9N-PL_3N	PA(A)_9N-PL
Nucleotide sequence of random linking peptide	TAC TGG TTG	AAA CTA GCT AAC AAC	TTG	GGT GAG ATG CAC	GAC TTT ATT
Amino acid sequence of random linking peptide	Y W L	K L A N N	L	G E M H	D F I
Number of clones selected with hIgM (11)*	4	2	3	1	1
Number of clones selected with hIgA (10)	5	2	2	1	0

*: Number of sequenced phage clones; Underlined and italic parts represent the nucleotide and amino acid sequences of linking peptide followed the second domain. 3N, 6N and 9N: the sequence of random linking peptides composed of three, six and nine nucleotides. Single letter abbreviations of amino acids: A, Ala; D, Asp; E, Glu; F, Phe; G, Gly; H, His; I, Ile; K, Lys; L, Leu; M, Met; N, Asn; W, Trp; Y, Tyr.