Summary.
We examined the nature of the posttranslational modification of bovine cytochrome b 561, a membrane-spanning protein and an essential component of neuroendocrine secretory vesicles. Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS) showed two populations in the partially digested fragments of cytochrome b 561, which were obtained by controlled treatment of cytochrome b 561-proteoliposomes with trypsin. One population, containing the posttranslationally modified amino-terminal region, showed molecular masses which were by about 40 Da larger than the theoretical molecular masses. The other population, without the modified amino-terminal region, showed a reasonable matching with the theoretical masses. This result suggested that the posttranslational modification occurred only in the amino-terminal region. The amino-terminal peptide was isolated by tryptic peptide mapping followed by treatment with acylamino-acid-releasing enzyme. Amino acid sequence and MALDI-TOF-MS analyses of the amino-terminal peptide showed that the initial Met residue was acetylated. There was no other posttranslational modification in the amino-terminal region, such as covalent fatty acylation through an ester linkage to Ser or Thr residues.
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Received May 9, 2002; accepted July 26, 2002; published online May 21, 2003
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ID="*" Correspondence and reprints: Department of Molecular Science, Graduate School of Science and Technology, Kobe University, Rokkodai-cho 1-1, Nada-ku, Hyogo 657-8501, Japan.
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Nakamura, M., Takeuchi, F. & Tsubaki, M. Cytochrome b 561 is not fatty acylated but acetylated at amino terminus in chromaffin vesicle membranes: an approach for the identification of posttranslational modification of transmembrane proteins. Protoplasma 221, 41–46 (2003). https://doi.org/10.1007/s00709-002-0062-3
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DOI: https://doi.org/10.1007/s00709-002-0062-3