Antigenic, molecular and functional heterogeneity of Clara cell secretory proteins in the rat

Gurmukh Singh, Sikandar L. Katyal, Shirley A. Gottron

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Abstract

In an earlier publication we had reported the preparation of a rabbit antiserum specific for rat Clara cell secretory proteins. This rabbit anti-rat Clara cell serum was found to react with two proteins in rat lung lavage by crossed-immmunoelectrophoresis. Immunoblotting of rat lung lavage proteins, after sodiium dodecylsulphate (SDS) polyacrylamide gel electrophoresis, disclosed three bands of reactivity with anti-Clara cell serum. The relative molecular masses of these three proteins were about 200 (protein A) 55 (protein B) and about 12 kDa (protein C). Anti-Clara cell antibodies eluted from Sepharose-4B-linked protein C (as well as the antiserum raised by immunizing rabbits with protein C) reacted with proteins A and C. Anti-Clara cell antiserum unbound to proteins A and C (as well as antiserum raised by immunizing rabbits with protein B) reacted with protein B only. In non-SDS polyacrylamide gel electrophoresis, protein B migrated as a single band, slightly cathodic to albumin; protein C resolved into three bands, all anodic to albumin. Immunoblots of isoelectric focusing gels showed three bands (pI 5.2-5.7) that reacted with antibody to protein C, and four bands corresponding to protein B were seen in the pI range 4.6-5.0. As determined by immunoperoxidase staining of paraformaldehyde fixed methacrylate embedded 1 μm thick sections of rat lung, protein(s) A (and protein C) and protein B were present in the same cells and in the same granules. Protein B was resistant to trypsin digestion, whereas proteins A and C were readily degraded by trypsin. Rat Clara cell secretory proteins consist of at least two antigenic types that appear to be functionally distinct, and each antigenic type displays charge microheterogeneity.

Original languageEnglish (US)
Pages (from-to)156-163
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume829
Issue number2
DOIs
Publication statusPublished - Jun 10 1985
Externally publishedYes

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Keywords

  • (Rat lung)
  • Clara cell
  • Immunoblotting
  • Secretory protein
  • Trypsin digestion

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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