Structure of the Legionella Effector, lpg1496, Suggests a Role in Nucleotide Metabolism

• Published in: The Journal of biological chemistry 2015-10, Vol.290 (41), p.24727-24737
• Main Authors: Wong, Kathy, Kozlov, Guennadi, Zhang, Yinglu, Gehring, Kalle
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - metabolism; Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Binding Sites; Cyclic AMP - metabolism; Legionella pneumophila - metabolism; Models, Molecular; Molecular Sequence Data; nuclear magnetic resonance (NMR); Nucleotides - metabolism; pneumonia; protein structure; Protein Structure and Folding; Protein Structure, Tertiary; protein-nucleic acid interaction; structural biology; virulence factor; x-ray crystallography
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.671263

Pathogenic Gram-negative bacteria use specialized secretion systems that translocate bacterial proteins, termed effectors, directly into host cells where they interact with host proteins and biochemical processes for the benefit of the pathogen. lpg1496 is a previously uncharacterized effector of Legionella pneumophila, the causative agent of Legionnaires disease. Here, we crystallized three nucleotide binding domains from lpg1496. The C-terminal domain, which is conserved among the SidE family of effectors, is formed of two largely α-helical lobes with a nucleotide binding cleft. A structural homology search has shown similarity to phosphodiesterases involved in cleavage of cyclic nucleotides. We have also crystallized a novel domain that occurs twice in the N-terminal half of the protein that we term the KLAMP domain due to the presence of homologous domains in bacterial histidine kinase-like ATP binding region-containing proteins and S-adenosylmethionine-dependent methyltransferase proteins. Both KLAMP structures are very similar but selectively bind 3′,5′-cAMP and ADP. A co-crystal of the KLAMP1 domain with 3′,5′-cAMP reveals the contribution of Tyr-61 and Tyr-69 that produces π-stacking interactions with the adenine ring of the nucleotide. Our study provides the first structural insights into two novel nucleotide binding domains associated with bacterial virulence. Background: lpg1496 is a member of the SidE family of Legionella pneumophila and involved in bacterial virulence. Results: The three domains of lpg1496 have been crystallized and characterized in nucleotide-bound and free states. Conclusion: The effector lpg1496 is likely involved in nucleotide metabolism. Significance: This is the first structural characterization of KLAMP and SidE domains.