Autoacetylation of Purified Calreticulin Transacetylase Utilizing Acetoxycoumarin as the Acetyl Group Donor

Erratum to: Appl Biochem Biotechnol DOI 10.1007/s12010-008-8357-2

In the original paper, the figures were incorrectly labeled. The figures and their corresponding legends should appear as follows.

Figures 1, 2, 3, 4, 5 and 6

Fig. 1

Sequences of calnexin (PDB ID 1JHN), CR P-domain (PDB ID 1HHN), CR signal peptide sequence (PDB ID 2CLR) and human CR sequence swissprot accession no. P27797 are aligned using InsightII/Homology and displayed by BOXSHADE program (http://www.ch.embnet.org/software/BOX_form.html). Shaded residues denote identity (Black) or close similarity (Gray) between sequences

Fig. 2

Effect of Ca²⁺ on CRTAase catalyzed acetylation of NADPH cytochrome P-450 reductase by DAMC. Lane 1 Prestained molecular weight markers; lane 2 CRTAase +DMSO; lane 3 NADPH cytochrome P-450 reductase + DAMC; lane 4 CRTAase + DMSO + CaCl₂ (5 μM) +NADPH cytochrome P-450 reductase; lane 5 CRTAase + DAMC; lane 6 CRTAase + CaCl₂ (5 μM) + DAMC; lane 7 CRTAase + CaCl₂ (5 μM) + DAMC+ NADPH cytochrome P-450 reductase; lane 8 CRTAase + DAMC + NADPH cytochrome P-450 reductase

Fig. 3

Tandem mass spectra of selected CR tryptic peptides containing acetyl-lysine. residue numbers shown in boldface type above and below the peptide sequences indicate detected collision-induced dissociation fragments for y-series (C-terminal) and b-series (N-terminal) ions, respectively. (a) Sequence SDFGkFVLSSGK (Corresponding to residues 45–55 of CR) observed in the tryptic digest of CR, the ion at m/z 648.4 was generated by loss of water from doubly charged precursor; (b) sequence NVLINkDIR. (Corresponding to residues 154–162 of CR) peak at m/z 554.9 represents the ion due to loss of water in the doubly charged precursor; (c) sequence kIKDPDASKPEDWDER (Corresponding to residues 207–222 of CR) observed in the tryptic digest of CR. MS/MS m/z 657.9 (3+). Asterisk corresponds to internal fragments

Fig. 4

The predicted structure of CR is represented in Kabsch–Sander secondary structure with α-helices in red and β-sheets in yellow. The modified lysine residues are in stick representation with standard atom colors. The figure was prepared using Pymol software [43]

Fig. 5

Comparison of intermolecular H-bonds (dotted lines) of lysines with glutamate and aspartate residues in non-acetylated (a) and acetylated (b) CR, after energy minimization. The amino acid residues are rendered in sticks with standard atom colors. Loss of H-bonds between Lys-62 and Glu-25, Lys-64 and Asp-63 also in Lys-48 and Glu-39 was observed due to neutralization of the positively charged lysine residue by acetylation.The acetylated lysine residues of N-domain are highlighted here. The figure was generated using InsightII program [26]

Fig. 6

Comparison of non-acetylated (a) and acetylated (b) CR P-domain lysines. Loss of H-bonds between Lys-206 and Glu-240, Lys-238 and Glu-270 as well as Lys-209 and Glu-221 was observed due to N-ε-acetylation of lysine residues. Also, increase in the intermolecular distances between acetyl-lysine (AcLys-238) and glutamate (Glu-270) is observed. The amino acid residues are rendered in sticks with standard atom colors. The amino acid residues rendered in sticks with standard atom colors and figure is realized using InsightII program [26]