Elucidation of a minimal immunoreactive site of vertebrate calmodulin

Linda J. Van Eldik, D. Martin Watterson, Kam Fook Fok, Bruce W. Erickson

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12 Scopus citations


The heptapeptide AsnTyrGluGluPheValGlnNH2 corresponding to residues 137-143 of vertebrate calmodulin is as immunoreactive as the entire 148-residue protein. A reproducible and rapid procedure for producing antisera against vertebrate calmodulin has been previously described (L. J. Van Eldik and D. M. Watterson (1981) J. Biol. Chem. 256, 4205-4210). Most of the antisera elicited by this method react with a major immunoreactive region (residues 127-144) in the COOH-terminal domain of vertebrate calmodulin. In this report, the minimum segment of calmodulin required for reactivity with an antiserum that readily distinguishes various types of calmodulins is defined. These studies demonstrate that a linear segment of seven amino acid residues shows a competition curve in radioimmunoassay resembling the competition curve of intact calmodulin. This heptapeptide is the smallest calmodulin segment and the only sevenresidue segment in the 135-145 region that shows quantitative immunoreactivity with the anti-calmodulin serum. These data demonstrate that this heptapeptide is a major immunoreactive site of calmodulin. However, when this immunoreactive site heptapeptide is conjugated to a carrier and injected into rabbits, it does not elicit antisera that react with the native protein. These studies demonstrate that quantitative immunoreactivity of antisera produced in animals can be found in small peptide segments and that, for calmodulin, the requirements for production of anti-peptide antibodies that react with the native protein molecule are not as simple as surface exposure of the peptide region.

Original languageEnglish
Pages (from-to)522-533
Number of pages12
JournalArchives of Biochemistry and Biophysics
Issue number2
StatePublished - Dec 1983

Bibliographical note

Funding Information:
i This work was supported in part by National Institutes of Health Grants AI 18362 (to B.W.E.), RR 07065 (to Rockefeller Univ.), GM 30861, and 30953 (to D.M.W.), National Science Foundation Grant PCM 8242875 (to D.M.W.), and American Cancer Society Institutional Research Grant No. IN-25V (to L.V.E.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.C.C. Section 1734 solely to indicate this fact. ’ To whom correspondence should be addressed. ‘Postdoctoral fellow of the Muscular Dystrophy Association.

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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