Differential Susceptibility of Human IgA Immunoglobulins to Streptococcal IgA Protease (original) (raw)
Research Article Free access | 10.1172/JCI107875
Gastroenterology Unit, Department of Medicine, Tufts-New England Medical Center Hospital, Boston, Massachusetts 02111
Gastroenterology Unit, Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts 02111
Naval Medical Research Institute, Bethesda, Maryland 20014
Department of Microbiology, Mount Sinai School of Medicine of the City University of New York, 10029
Find articles by Plaut, A. in:PubMed |Google Scholar
Gastroenterology Unit, Department of Medicine, Tufts-New England Medical Center Hospital, Boston, Massachusetts 02111
Gastroenterology Unit, Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts 02111
Naval Medical Research Institute, Bethesda, Maryland 20014
Department of Microbiology, Mount Sinai School of Medicine of the City University of New York, 10029
Find articles by Wistar, R. in:PubMed |Google Scholar
Gastroenterology Unit, Department of Medicine, Tufts-New England Medical Center Hospital, Boston, Massachusetts 02111
Gastroenterology Unit, Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts 02111
Naval Medical Research Institute, Bethesda, Maryland 20014
Department of Microbiology, Mount Sinai School of Medicine of the City University of New York, 10029
Find articles by Capra, J. in:PubMed |Google Scholar
Published December 1, 1974 -More info
Published December 1, 1974 -Version history
IgA protease, a proteolytic enzyme found in human saliva and colonic fluid, hydrolyzes human serum IgA immunoglobulins to yield Fabα and Fcα fragments. The enzyme is produced by organisms in the normal human microflora and can be purified from culture filtrates of the common human oral organism Streptococcus sanguis (American Type Culture Collection no. 10556). IgA protease is inactive against all other protein substrates examined including the other classes of human immunoglobulins. The role of this enzyme in affecting the function of the secretory IgA immune system is unknown.
To further characterize and explain this unusual substrate specificity, the susceptibility of 31 human IgA myeloma proteins of both subclasses was investigated. 16 IgA1 and 15 IgA2 myeloma paraproteins were treated with enzyme and the extent of proteolysis was determined by cellulose actate electrophoresis, immunoelectrophoresis, polyacrylamide gel electrophoresis, and column chromatography. All IgA1 proteins were enzymatically cleaved to Fabα and Fcα fragments, but all IgA2 proteins were resistant, yielding no fragments after prolonged enzymatic treatment. N-terminal amino acid sequence analysis of the purified Fcα fragment of a single IgA1 paraprotein was as follows: Thr-Pro-Ser-Pro-?-Thr-Pro-Pro-Thr-Pro-Ser-Pro-Ser. Comparison of this sequence to that reported for the IgA1 heavy chain shows that the enzyme-susceptible peptide bond is a Pro-Thr in the IgA1 hinge region. The most likely explanation of the resistance of the IgA2 subclass to IgA protease is a deletion in the heavy chain which commences with the critical threonine of the susceptible Pro-Thr bond.
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