期刊
METALLOMICS
卷 12, 期 2, 页码 280-289出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9mt00200f
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资金
- UGC, Government of India
Candidatus Liberibacter asiaticus (CLas), a phloem-limited unculturable Gram-negative bacterium, causes citrus greening disease. The proteome analysis of CLas showed the presence of a heavy metal permease and Co/Zn/Cd cation exporter system. However, there is no designated metal uptake protein specific for the heavy metal permease in CLas. One of the metal uptake proteins, designated as CLas-ZnuA2, in our previous studies, showed a lower metal-binding affinity for Mn2+ and Zn2+ and was postulated to bind and transport metals rather non-specifically. The present study focused on the characterization of the heavy metal binding properties of CLas-ZnuA2 using SPR, CD, DSC and crystallographic studies. The crystal structure analysis of Cd2+ bound CLas-ZnuA2 showed octahedral geometry for Cd2+ binding as compared to a non-preferred square-pyramidal geometry for Mn2+ and Zn2+ binding in earlier reported crystal structures. In SPR analysis, the binding affinities of 4.7 x 10(-6) M, 7.2 x 10(-6) M, 5.3 x 10(-5) M and 4.3 x 10(-5) M for Hg2+, Cd2+, Ba2+ and Co2+ respectively were higher as compared to earlier reported values for Mn2+ and Zn2+. Likewise, CD and DSC analysis showed relatively higher thermal stability for CLas-ZnuA2 on heavy metal binding. Taken together with the expression of the permease and exporter system for heavy metals, our results indicate that CLas-ZnuA2 may be involved in sequestering and transport of various transition divalent metals in environmentally stressed conditions.
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