Specific recognition of protein carboxy-terminal sequences by natural IgM antibodies in normal serum.
Our previous study indicated that normal serum contains complement-fixing natural IgM antibodies reacting with a large variety of randomly generated protein carboxy-termini. Here we show that the "carboxy-terminal" IgM (C-IgM) antibodies specifically react with short peptide sequences located immediately at the protein carboxy-terminus. The specificity of C-IgM-peptide interactions is tentatively defined by three to four amino acid residues. All carboxy-terminal peptides in a large peptide library apparently react with C-IgM antibodies. Immobilized synthetic peptides also react with C-IgM antibodies. No interaction of C-IgM antibodies with internal peptide sequences has been observed. C-IgM antibodies are present in germ-free and in athymic adult rats and are absent in newborn rats. The natural ubiquity of protein carboxy-termini in biological structures suggests that C-IgM could play an important role in antigen clearance and presentation to the immune system. From a practical viewpoint, the recognition of carboxy-terminal peptides by complement-fixing C-IgM antibodies has profound implications for the use of peptide- and protein-derivatized delivery vehicles and artificial materials.
Sokoloff
A V
AV
Department of Pediatrics, University of Wisconsin, Madison, Wisconsin 53705, USA.
Bock
I
I
Zhang
G
G
Hoffman
S
S
Dama
J
J
Ludtke
J J
JJ
Cooke
A M
AM
Wolff
J A
JA
D000818:Animals; D000917:Antibody Formation; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions / Q000276:immunology; D017123:Bacteriophage T7 / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D004926:Escherichia coli / Q000235:genetics; D005822:Genetic Vectors; D007075:Immunoglobulin M / Q000276:immunology*; D008024:Ligands; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology*; D019151:Peptide Library; D051381:Rats; D017207:Rats, Sprague-Dawley
D000939:Epitopes; D007075:Immunoglobulin M; D008024:Ligands; D010446:Peptide Fragments; D019151:Peptide Library