Autoacetylation of purified calreticulin transacetylase utilizing acetoxycoumarin as the acetyl group donor

Seema Bansal, Prija Ponnan, Hanumantharao G. Raj, Susan T. Weintraub, Madhu Chopra, Ranju Kumari, Daman Saluja, Ajit Kumar, Tapesh K. Tyagi, Prabhjot Singh, Ashok K. Prasad, Luciano Saso, Ramesh C. Rastogi, Virinder S. Parmar

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Our earlier reports documented that calreticulin, a multifunctional Ca 2+-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase (CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property of CRTAase by immunoblotting and mass spectrometry. Ca2+ was found to inhibit CRTAase activity. The inhibition of both autoacetylation of CRTAase as well as acetylation of the receptor protein was apparent when Ca2+ was included in the reaction mixture as visualized by interaction with anti-acetyl lysine antibody. The acetylation of lysines residues: -48, -62, -64, -153, and -159 in N-domain and -206, -207, -209, and -238 in P-domain of CRTAase were located by high-performance liquid chromatography-electronspray ionization tandem mass spectrometry. Further, computer assisted protein structure modeling studies were undertaken to probe the effect of autoacetylation of CRTAase. Accordingly, the predicted CRTAase 3D model showed that all the loop regions of both N- and P-domain bear the acetylated lysines. Energy minimization of the acetylated residues revealed charge neutralization of lysines due to the N-ε-acetylation which may facilitate the interaction of CRTAase with the protein substrate and the subsequent transacetylase action.

Original languageEnglish (US)
Pages (from-to)285-298
Number of pages14
JournalApplied Biochemistry and Biotechnology
Issue number2
StatePublished - May 2009


  • Acetoxycoumarin
  • Calreticulin
  • Mass spectrometry
  • Protein acetylation
  • Protein acetyltransferase

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Biochemistry
  • Applied Microbiology and Biotechnology
  • Molecular Biology


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