title: 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.
abstract: BACKGROUND
  Protein A, protein G and protein L are three well-defined immunoglobulin (Ig)-binding proteins (IBPs), which show affinity for specific sites on Ig of mammalian hosts. Although the precise functions of these molecules are not fully understood, it is thought that they play an important role in pathogenicity of bacteria. The single domains of protein A, protein G and protein L were all demonstrated to have function to bind to Ig. Whether combinations of Ig-binding domains of various IBPs could exhibit useful novel binding is interesting.
  
  
  RESULTS
  We used a combinatorial phage library which displayed randomly-rearranged various-peptide-linked molecules of D and A domains of protein A, designated PA(D) and PA(A) respectively, B2 domain of protein G (PG) and B3 domain of protein L (PL) for affinity selection with human IgG (hIgG), human IgM (hIgM), human IgA (hIgA) and recombinant hIgG1-Fc as bait respectively. Two kinds of novel combinatorial molecules with characteristic structure of PA(A)-PG and PA(A)-PL were obtained in hIgG (hIgG1-Fc) and hIgM (hIgA) post-selection populations respectively. In addition, the linking peptides among all PA(A)-PG and PA(A)-PL structures was strongly selected, and showed interestingly divergent and convergent distribution. The phage binding assays and competitive inhibition experiments demonstrated that PA(A)-PG and PA(A)-PL combinations possess comparable binding advantages with hIgG/hIgG1-Fc and hIgM/hIgA respectively.
  
  
  CONCLUSIONS
  In this work, a combinatorial phage library displaying Ig-binding domains of protein A, protein G, or protein L joined by various random linking peptides was used to conducted evolutional selection in vitro with four kinds of Ig molecules. Two kinds of novel combinations of Ig-binding domains, PA(A)-PG and PA(A)-PL, were obtained, and demonstrate the novel Ig binding properties.
authors.affiliation: Department of Microbiology, State Key Laboratory of Medical Immunology, Second Military Medical University, Shanghai 200433, PR China. yanghua97065@yahoo.com.cn
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Lian-Qing
authors.initials: LQ
authors.lastname: Li
authors.forename: Xia
authors.initials: X
authors.lastname: Zhou
authors.forename: Qiu-Li
authors.initials: QL
authors.lastname: Chen
authors.forename: Wen-Ting
authors.initials: WT
authors.lastname: Liao
authors.forename: Zong-Mei
authors.initials: ZM
authors.lastname: Wen
authors.forename: Shao-Hua
authors.initials: SH
authors.lastname: Jiang
authors.forename: Rong
authors.initials: R
authors.lastname: Xu
authors.forename: Jian-An
authors.initials: JA
authors.lastname: Jia
authors.forename: Xin
authors.initials: X
authors.lastname: Pan
authors.forename: Zhong-Tian
authors.initials: ZT
authors.lastname: Qi
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism*; D001667:Binding, Competitive; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology / Q000378:metabolism*; D019151:Peptide Library; D016415:Sequence Alignment; D013205:Staphylococcal Protein A / Q000276:immunology / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C055047:Ig L-binding protein, Peptostreptococcus; C034284:IgG Fc-binding protein, Streptococcus; D007136:Immunoglobulins; D019151:Peptide Library; D013205:Staphylococcal Protein A