雖然幽門螺旋桿菌(Helicobacter pylori)有能力適應多變的生存環境,成功的繁殖在胃黏膜上,然而在幽門螺旋桿菌的基因組裡,卻只有少數的基因調控因子。而調控因子之一， CsrA ( carbon storage regulator; locus tag:HP1442; GI:15646051) 對於幽門螺旋桿菌處於氧化作用頻繁的環境壓力下，有著維持其活動能力與生存的重要角色。若缺乏了CsrA，則由氧化環境所引發的napA及ahpC基因表現，由酸環境所引發的napA、cagA、vacA、fur基因表現，以及由熱所引發的napA、groESL、 hspR等等，全都會失去了調控。並且在老鼠感染模型的實驗裡可以見到，若幽門螺旋桿菌菌株本身的csrA基因無法表現，則將大大減低其毒性因子，使得感染率下降。因此，csrA對於幽門螺旋桿菌的生理機能、及對環境的適應調節有著莫大的重要性。更深入的說，CsrA 的作用機制發生在後轉錄階段( post-transcriptional level )，透過與目標訊息核醣核酸(mRNA)結合、或降低mRNA穩定性，使其無法進行轉譯(translation)而產生功能性的蛋白質，由此來達到調節的功能。為了提供CsrA(HP1442)的蛋白質結構，並找出與mRNA結合的區塊(binding domain)，我們以核磁共振光譜儀來解出HP1442的蛋白質結構，並試圖找出其鍵結專一性(binding specific)的關鍵所在。

Although successful and persistent colonization of the gastric mucosa depends on the ability to respond to changing environmental conditions and co-ordinate the expression of virulence factors during the course of infection, Helicobacter pylori possesses relatively few transcriptional regulators. Among these regulators csrA ( carbon storage regulator; locus tag:HP1442; GI:15646051) was necessary for full motility and survival of H. pylori under conditions of oxidative stress. Loss of csrA expression deregulated the oxidant-induced transcriptional responses of napA and ahpC, the acid induction of napA, cagA, vacA, the urease operon, and fur, as well as the heat shock responses of napA, groESL and hspR. Finally, H. pylori strains deficient in the production of CsrA were significantly attenuated for virulence in a mouse model of infection. Therefore, csrA has a broad role in regulating the physiology of H. pylori in response to environment stimuli. Deeply to say, CsrA appear to mediate its effect in H. pylori at the post-transcriptional level by influencing the processing and translation of target transcripts, with minimal effect on the stability of the target mRNAs. In order to find out the mechanism of mRNA binding, we use NMR spectroscopy to determine the solution structure of HP1442 and attempt to propose the crucial residues for specificity.

1. Lin, J.T., et al., Seroprevalence study of Helicobacter pylori infection in patients with gastroduodenal diseases. J Formos Med Assoc, 1994. 93(2): p. 122-7

2. Blaser, M.J., Helicobacter pylori : its role in disease. Clin Infect Dis, 1992. 15(3): p. 386-91

3. Blaser, M.J., Helicobacter pylori and the pathogenesis of gastroduodenal inflammation. J Infect Dis, 1990. 161(4): p. 626-33

4. Peek, R.M., Jr. and M.J. Blaser, Pathophysiology of Helicobacter pylori-induced gastritis and peptic ulcer disease. Am J Med, 1997. 102(2): p.200-7

5. Suerbaum, S., and Michetti, P. (2002) Helicobacter pylori infection. N Engl J Med 347: 1175–1186.

6. Tomb, J.F., White, O., Kervalage, A.R., Clayton, R.A., Sutton, G.G., Fleischmann, R.D., et al. (1997) The complete genome sequence of the gastric pathogen Helicobacter pylori. Nature 388: 539–547.

7. Alm, R.A., Ling, L.S., Moir, D.T., King, B.L., Brown, E.D., Doig, P.C., et al. (1999) Genomic-sequence comparison of two unrelated isolates of the human gastric pathogen Helicobacter pylori. Nature 397: 176–180.

8. Berg, D.E., Hoffman, P.S., Appelmelk, B.J., and Kusters, J.G. (1997). The Helicobacter pylori genome sequence: genetic factors for long life in the gastric mucosa. Trends Microbiol 5: 468–474.

9. Spiegelhalder, C., Gerstenecker, B., Kersten, A., Schiltz, E., and Kist, M. (1993) Purification of Helicobacter pylori superoxide dismutase and cloning and sequencing of the gene. Infect Immun 61: 5315–5325.

10. Skouloubris, S., Thiberge, J.M., Labigne, A., and De Reuse, H. (1998) The Helicobacter pylori UreI protein is not involved in urease activity but is essential for bacterial survival in vivo. Infection Immunity 66: 4517–4521.

11. Ramarao, N., Gray-Owen, S.D., and Meyer, T.F. (2000) Helicobacter pylori induces but survives the extracellular release of oxygen radicals from professional phagocytes using its catalase activity. Mol Microbiol 38: 103–113.

12. Bijlsma, J.J., Waidner, B., van Vliet, A.H., Hughes, N.J., Hag, S., Bereswill, S., et al. (2002) The Helicobacter pylori homologue of the ferric uptake regulator is involved in acid resistance. Infect Immun 70: 606–611.

13. Romeo, T., Gong, M., Liu, M.Y., and Brun-Zinkernagel, A. (1993) Identification and molecular characterization of csrA, a pleiotropic gene from Escherichia coli that effects glycogen biosynthesis, gluconeogenesis, cell size, and surface properties. J Bacteriol 175: 4744–4755.

14. Liu, M.Y., Yang, H., and Romeo, T. (1995) The product of the pleiotropic Escherichia coli gene csrA modulates glycogen biosynthesis via effects on mRNA stability. J Bacteriol 177: 2663–2672.

15. Romeo, T. (1998) Global regulation by the small RNA-binding protein CsrA and the non-coding RNA molecule CsrB. Mol Microbiol 29: 1321–1330.

16. Wei, B.L., Brun-Zinkernagel, A., Simecka, S.W., Prub, B.M., Babitzke, P., and Romeo, T. (2001) Positive regulation of motility and flhDC expression by the RNAbinding protein CsrA of Escherichia coli. Mol Microbiol 40: 245–256.

17. Baker, C.S., Morozov, I., Suzuki, K., Romeo, T., and Babitzke, P. (2002) CsrA regulates glycogen biosynthesis by preventing translation of glgC in Escherichia coli. Mol Microbiol 44: 1599–1610.

18. Jackson, D.W., Suzuki, K., Oakford, L., Simecka, J.W., Hart, M.E., and Romeo, T. (2002) Biofilm formation and dispersal under the influence of the global regulator CsrA of Escherichia coli. J Bacteriol 184: 290–301.

19. C. Zwahlen, P. Legault, S.J.F. Vincent, J. Greenblatt, R. Konrat &
L.E. Kay, J. Am. Chem. Soc. 119 6711-6721 (1997)

20. A.L. Breeze, Prog. NMR Spectrosc. 36, 323-372 (2000)

21. Herrmann, T., Güntert, P. & Wüthrich, K. (2002). Protein NMR structure determination with automated NOE assignment using the new software CANDID and the torsion angle dynamics algorithm DYANA. J. Mol. Biol. 319, 209-227.

22. Faye M. Barnard, Michael F. Loughlin, Hernan P. Fainberg, Michael P. Messenger, David W. Ussery, Paul Williams and Peter J. Jenks. (2004) Global regulation of virulence and the stress response by CsrA in the highly adapted human gastric pathogen Helicobacter pylori. Molecular Microbiology 51 (1): 15–32

23. Gabriel Cornilescu, Frank Delaglio, and Ad Bax. Protein backbone angle restraints from searching a database for chemical shift and sequence homology J. Biomol. NMR, 13 (1999) 289-302

24. D.S. Wishart and B.D. Sykes, The 13-C Chemical Shift Index: A Simple Method for the Identification of Protein Secondary Structure using 13-C Chemical Shift Data, J. Biomol. NMR.

25. Andrade, M.A., P. Chacón, J.J. Merelo and F. Morán. 1993. Prot. Eng., 6,
383-390

26. Gutie´rrez et al., Journal of bacteriology , May 2005 (187)2496-3501