Oral Presentation 2014 International Biophysics Congress

The crystal structure of a membrane bound endotoxin modifying enzyme from pathogenic Neisseria spp (#208)

Anandhi Anandan 1 , Susannah Piek 1 , Isabel Moaes 2 , Charlene M. Kahler 1 , Alice Vrielink 1
  1. Univesity of Western Australia, Crawley, WA, Australia
  2. Membrane Protein Laboratory, Didcot, UK

Endotoxins from pathogenic Neisseria spp. are composed of a LipidA moiety, which can be modified through the addition of phosphoethanolamine (PEA) by the enzyme lipopolysaccharide phosphoethanolamine transferase (LptA) (1). LptA is an integral membrane protein consisting of a transmembrane domain and a periplasmic soluble globular domain. LptA catalyses the hydrolysis of PEA from phosphatidylethanolamine and transfers PEA to lipid A at the 1 or 4’ positions. Various studies have provided evidence that the PEA decoration of lipid A plays a vital role in determining the interaction of the pathogen with the host immune system and disease progression. Furthermore, the modification of the endotoxin by the addition of PEA onto Lipid A alters the charge on the bacterial outer membrane which reduces resistance to host complement mediated killing (2). Inhibition of PEA modification of lipid A increases the susceptibility of neisserial pathogens to naturally occurring cationic antimicrobial peptides and cationic antibiotics such as polymyxin (3). The inhibition of LptA can therefore extend the effectiveness of currently existing antibiotics. Based on these observations we undertook structural studies of LptA from Neisseria with the aim of pursuing a structure guided drug design approach to develop inhibitors of LptA that will assist in controlling bacterial infection and transmission. LptA was expressed in a recombinant E. coli expression system, purified to homogeneity and crystallized for structural studies. The 2.75Å resolution crystal structure provides insights into the mechanism of substrate binding and catalysis of the enzyme suggesting possible conformational changes during catalysis.