ELUCIDATION OF THE PRIMARY STRUCTURE OF THE LANTIBIOTIC EPILANCIN K7 FROM STAPHYLOCOCCUS-EPIDERMIDIS K7 - CLONING AND CHARACTERIZATION OF THE EPILANCIN-K7-ENCODING GENE AND NMR ANALYSIS OF MATURE EPILANCIN K7

Lantibiotics are bacteriocins that contain unusual amino acids such as lanthionines and alpha,beta-didehydro residues generated by posttrans lational modification of a ribosomally synthesized precursor protein. The structural gene encoding the novel lantibiotic epilancin K7 from S taphylococcus epidermidis K7 was cloned and its nucleotide sequence wa s determined. The gene, which was named elkA, codes for a 55-residue p reprotein, consisting of an N-terminal 24-residue leader peptide, and a C-terminal 31-residue propeptide which is posttranslationally modifi ed and processed to yield mature epilancin K7. In common with the type -A lantibiotics nisin A and nisin Z, subtilin, epidermin, gallidermin and Pep5, pre-epilancin K7 has a so-called class-Al leader peptide. Do wnstream and upstream of the elkA gene, the starts of two open-reading -frames, named elkP and elkT, were identified. The elkP and elkT genes presumably encode a leader peptidase and a translocator protein, resp ectively, which may be involved in the processing and export of epilan cin K7. The amino acid sequence of the unmodified pro-epilancin K7, de duced from the elkA gene sequence, is in full agreement with the amino acid sequence of mature epilancin K7, determined previously by means of NMR spectroscopy [van de Kamp, M., Horstink, L. M., van den Hooven, M. W., Konings, R. N. M., Hilbers, C. W., Sahl, H.-G., Metzger, J. W. and van de Ven, F. J. M. (1995) Eur. J. Biochem. 227, 757-771]. The f irst residue of mature epilancin K7 appears to be modified in a way th at has not been described for any other lantibiotic so far. NMR experi ments show that the elkA-encoded serine residue at position +1 of pro- epilancin K7 is modified to a 2-hydroxypropionyl residue in the mature protein.