The origin of cecropins; implications from synthetic peptides derived fromribosomal protein L1

We recently showed that Helicobacter pylori grown on plates produce cecropi n-like antibacterial peptides to which H. pylori is resistant. This antibac terial activity was traced to fragments from the N-terminus of ribosomal pr otein L1 (Putsep et al,, Nature, April 22, 1999), The evolutionary suggesti on from this finding has now been extended by the synthesis of eight peptid es with sequences taken from the N-terminus of ribosomal protein L1 (RpL1) of five different species. Two peptides of different length derived from H. pylori RpL1 showed a potent antibacterial activity, while a peptide with t he sequence from Escherichia coli was 20 times less active. Like cecropins the H. pylori peptides mere not cytolytic. We suggest that the cecropins ha ve evolved from ribosomal protein L1 of an ancestral intracellular pathogen that developed to a symbiont ending as an organelle. When the R1 gene move d into the host nucleus, a duplication provided a copy from which today cec ropins could have evolved. (C) 1999 Federation of European Biochemical Soci eties.