Tuesday, December 22, 2009

Peptide tagging and modification systems in prokaryotes: exploring the base of the iceberg

In a previous study, we had uncovered several prokaryotic systems encoding homologs of E1, E2 and Ub, pointing to the presence of ubiquitination-like systems in prokaryotes. We had also described several poorly characterized peptide modification systems involving E1-like enzymes. More recently, we uncovered the enzymatic basis of pupylation, a peptide tagging system found in some bacteria. In a comprehensive study, we now describe over 20 novel systems involved in peptide synthesis and modification, amine-utilization, secondary metabolite synthesis and potential peptide-tagging systems. These systems involve one or more enzymes of the ATP-grasp, the COOH-NH2 ligase and acetyltransferase fold.

Some highlights include:

1. A potential peptide-tagging system involving a circularly permuted ATP-grasp domain and circularly permuted glutamine synthetase-like ligase, an NTN-hydrolase fold peptidase and a
novel alpha helical domain.

2. The elucidation of the biochemical mechanism of key steps involved in the synthesis of various peptide antibiotics and cell surface polysaccharides like teichuronopeptides.

3. Discovering the first prokaryotic orthologs of the eukaryotic tyrosine tubulin ligases (TTL).

Watch this space for further details about some of these systems. For now, you may read the article here.