NMR Structure and Calcium-Binding Properties of the Tellurite Resistance Protein TerD from Klebsiella pneumoniae.

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NMR Structure and Calcium-Binding Properties of the Tellurite Resistance Protein TerD from Klebsiella pneumoniae.

NMR Structure and Calcium-Binding Properties of the Tellurite Resistance Protein TerD from Klebsiella pneumoniae.

J Mol Biol. 2010 Nov 25;

Authors: Pan YR, Lou YC, Seven AB, Rizo J, Chen C

The tellurium oxyanion, TeO(3)(2-), has been used in the treatment of infectious diseases caused by mycobacteria. However, many pathogenic bacteria show tellurite resistance. Several tellurite resistance genes have been identified, and these genes mediate responses to diverse extracellular stimuli, but the mechanisms underlying their functions are unknown. To shed light on the function of KP-TerD, a 20.5 kDa tellurite resistance protein from a plasmid of Klebsiella pneumoniae, we have determined its three-dimensional structure in solution using NMR spectroscopy. KP-TerD contains a beta-sandwich formed by two five-stranded beta-sheets and six short helices. The structure exhibits two negative clusters in loop regions on the top of the sandwich, suggesting that KP-TerD may bind metal ions. Indeed, thermal denaturation experiments monitored by circular dichroism and NMR studies reveal that KP-TerD binds Ca(2+). Inductively coupled plasma-optical emission spectroscopy shows that the binding ratio of KP-TerD to Ca(2+)is 1:2. EDTA titrations of Ca(2+)-saturated KP-TerD monitored by 1D NMR yield estimated dissociation constants of 18 nM and 200 nM for the two Ca(2+)-binding sites of KP-TerD. NMR structures incorporating 2 Ca(2+)ions define a novel bipartite Ca(2+)binding motif that is predicted to be highly conserved in TerD proteins. Moreover, these Ca(2+)-binding sites are also predicted to be present in two additional tellurite resistance proteins, TerE and TerZ. These results suggest that some form of Ca(2+)signaling plays a crucial role in tellurite resistance and in other responses of bacteria to multiple external stimuli that depend on the Ter genes.

PMID: 21112337 [PubMed - as supplied by publisher]



Source: PubMed