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Comparison of Iron‐Binding Ability Between Thr70‐NapA and Ser70‐NapA of Helicobacter pylori
Author(s) -
Shan Weiran,
Kung Hsiangfu,
Ge Ruiguang
Publication year - 2016
Publication title -
helicobacter
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.206
H-Index - 79
eISSN - 1523-5378
pISSN - 1083-4389
DOI - 10.1111/hel.12266
Subject(s) - napa , helicobacter pylori , chemistry , medicine , gastroenterology , biochemistry
Background The neutrophil‐activating protein (NapA) of Helicobacter pylori ( H. pylori ), with DNA ‐binding and iron seizing properties, is a fundamental virulence factor involved in H. pylori ‐related diseases. Compared with Ser70‐NapA strain, Thr70‐NapA strain is more intimately correlated with iron‐deficiency anemia. Methods To investigate whether two types of proteins differ in iron‐binding ability, mutated Thr70‐NapA and Ser70‐NapA strains were established. Isothermal titration calorimetry ( ITC ) method was conducted to measure the binding between the NapA protein and Fe 2+ . The structural changes of NapA protein were also tested during iron interaction by fast protein liquid chromatography ( FPLC ) and circular dichroism ( CD ) methods. DNA ‐binding assay was performed for evaluate the affinity of both mutated and wild types of NapA with DNA . Results Mutated Thr70‐NapA had higher iron‐binding ability than wild Ser70‐NapA. The structural stability of Thr70‐NapA was disrupted and became more active along with the rising concentration of Fe 2+ , whereas no similar association was observed between Ser70‐NapA and Fe 2+ level. When the iron/protein molar ratio ranged from 10 to 20, both Ser70‐NapA and Thr70‐NapA displayed weaker DNA ‐binding ability. Conclusions Thr70‐NapA has much stronger ability to sequester ferrous ion compared with Ser70‐NapA in H. pylori . In addition, the DNA ‐binding property of NapA is dependent upon the Fe 2+ concentration.