THE C-TERMINAL BISPHOSPHORYLATED PROENKEPHALIN-A-(209-237)-PEPTIDE FROM ADRENAL-MEDULLARY CHROMAFFIN GRANULES POSSESSES ANTIBACTERIAL ACTIVITY

The chromaffin granules have been shown to be an excellent model to st udy the processing of proenkephalin-A and chromogranins. Recently, we reported a study dealing with the processing of chromogranin B/secreto granin I and the occurrence of the C-terminal chromogranin B-derived p eptide 614-626 which was shown to have antibacterial activity [Strub, J. M., Garcia-Sablone, P., Looning, K., Taupenot, L., Hubert, P., Van Dorsselaer, A., Aunis, D. & Metz-Boutigue, M. H. (1995) Eur J. Biochem . 229, 356-368]. We also observed that this new antibacterial activity present in chromaffin granules was associated with other endogenous p rotein-derived fragments yet to be characterized. The present study re ports the isolation and characterization of a peptide which possesses antibacterial activity and which corresponds to the C-terminal 209-237 sequence of proenkephalin-A. A detailed study using microsequencing a nd matrix-assisted-laser-desorption time-of-flight mass spectrometry ( MALD-TOF MS) allowed us to correlate the antibacterial activity of thi s peptide named enkelytin (FAEPLPSEEEGE-SYSKEVPEMEKRYGGFM) with post-t ranslational modifications. Endogenous bisphosphorylated preen kephali n-A-(209-237) was active on Micrococcus luteus and Bacillus megaterium killing bacteria in the 0.2-0.4 mu M range but was inactive in simila r conditions towards Escherichia coli. Enkelytin shares sequence and s tructural similarities with the antibacterial C-terminal domain of dia zepam-binding inhibitor. According to this similarity, a prediction of secondary structure is proposed for enkelytin and discussed in relati on to its biological activity.