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Characterization of PPT_Ns, a Cyanobacterial Phosphopantetheinyl Transferase from Nodularia spumigena NSOR10

J. N. Copp,^1, A. A. Roberts,¹ M. A. Marahiel,² and B. A. Neilan^1*

School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington 2052, Sydney, Australia,¹ Fachbereich Chemie, Philipps-Universität, Marburg, Germany²

Received 10 December 2006/ Accepted 2 February 2007

The phosphopantetheinyl transferases (PPTs) are a superfamily of essential enzymes required for the synthesis of a wide range of compounds, including fatty acids, polyketides, and nonribosomal peptide metabolites. These enzymes activate carrier proteins in specific biosynthetic pathways by transfer of a phosphopantetheinyl moiety. The diverse PPT superfamily can be divided into two families based on specificity and conserved sequence motifs. The first family is typified by the Escherichia coli acyl carrier protein synthase (AcpS), which is involved in fatty acid synthesis. The prototype of the second family is the broad-substrate-range PPT Sfp, which is required for surfactin biosynthesis in Bacillus subtilis. Most cyanobacteria do not encode an AcpS-like PPT, and furthermore, some of their Sfp-like PPTs belong to a unique phylogenetic subgroup defined by the PPTs involved in heterocyst differentiation. Here, we describe the first functional characterization of a cyanobacterial PPT based on a structural analysis and subsequent functional analysis of the Nodularia spumigena NSOR10 PPT. Southern hybridizations suggested that this enzyme may be the only PPT encoded in the N. spumigena NSOR10 genome. Expression and enzyme characterization showed that this PPT was capable of modifying carrier proteins resulting from both heterocyst glycoplipid synthesis and nodularin toxin synthesis. Cyanobacteria are a unique and vast source of bioactive metabolites; therefore, an understanding of cyanobacterial PPTs is important in order to harness the biotechnological potential of cyanobacterial natural products.

Published ahead of print on 16 February 2007.

Present address: Biological Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand.