Chinese Journal of Magnetic Resonance ›› 2015, Vol. 32 ›› Issue (2): 308-317.doi: 10.11938/cjmr20150213

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The Extended Loop Reduces Ca2+-Binding Affinity on the Tellurite Resistance Protein TerZ from Klebsiella penumoniae

WEI Shu-yi,PAN Yun-ru,TSENG Tien-sheng,CHEN Chin-pan*   

  1. Institute of Biomedical Sciences, Taipei 11529, China
  • Received:2015-03-02 Revised:2015-05-08 Online:2015-06-05 Published:2015-06-05
  • About author:*Corresponding author: CHEN Chin-pan, Tel: +886-2-27899162, E-mail: bmchinp@ibms.sinica.tw.
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Abstract:

Tellurite (TeO32–), an oxyanion of tellurium, is highly toxic to most microorganisms. Several tellurite resistance genes (terZABCDEF) have been identified in many pathogenic bacteria. Previously, we determined the NMR solution structure of the tellurite resistance protein TerD and suggested that TerD may function as a calcium sensor in bacteria. TerZ, which shares 40% sequence identity with TerD, contains an extra 9-residue segment of L36FGSIFGGN44 and exhibits much weaker Ca2+-binding affinity. Interestingly, TerZdel in which the extra segment is deleted has comparable binding affinity to TerD. Based on chemical shift index and homology modeling results, it was revealed that the extra segment is unstructured and forms an extended loop, which may disturb the conformation of Ca2+-binding sites and also prevent Ca2+ from contacting its binding site, hence significantly reduce Ca2+-binding affinity.

Key words: Ca2+-binding protein, tellurite resistance, calcium sensor, chemical shift index, homology modeling

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