YuiI-dependent ferri-bacillibactin hydrolysis in Bacillus subtilis

MILTON T. STUBBS
Physikalische Biotechnologie
Institut für Biotechnologie
Martin-Luther-Universität Halle-Wittenberg
Kurt-Mothes-Str. 3
D-06120 Halle (Saale)
stubbs@biochemtech.uni-halle.de
http://www.biochemtech.uni-halle.de/biotechnologie/xray/

MOHAMED A. MARAHIEL
Fachbereich Chemie
Philipps-Universität Marburg
Hans-Meerwein-Straße
D-35032 Marburg
marahiel@chemie.uni-marburg.de
http://www.chemie.uni-marburg.de/~ak66/

The gram-positive model organism Bacillus subtilis produces the catecholic trilactone siderophore bacillibactin during iron starvation. Bacillibactin is assembled by the nonribosomal peptide synthetase DhbEBF [1,2]. After secretion and extracellular iron-complex formation, ferri-bacillibactin is imported into the cell by the FeuABC(YusV) ABC-transporter [3,4]. To release the iron from the siderophore, the trilactone cycle of ferri-bacillibactin is hydrolysed by the YuiI esterase [4]. A yuiI mutant exhibited impaired growth during iron starvation and displayed high intra- and extracellular (ferri)-bacillibactin accumulation. The protein sequence of YuiI is appr. 20 % identical to the IroE trilactone hydrolase of enteric bacteria. YuiI is conserved among both pathogenic and non-pathogenic Bacillus species. The protein was overproduced (yield appr. 30 mg/l) as recombinant His-tagged fusion and used for kinetic studies in vitro. YuiI was found to accept both bacillibactin and ferri-bacillibactin as substrates, however, the catalytic efficiency of trilactone hydrolysis was 25-fold higher when iron was complexed, confirming ferri-bacillibactin as the preferred substrate of YuiI. Currently, recombinant YuiI is tried to be crystallized to gain structural information about this trilactone hydrolase in interaction with its substrate. Since trilactone hydrolases are involved in the iron acquisition pathway in several important pathogens (such as pathogenic E. coli or Salmonella spp.), inhibition studies with non-hydrolyzable siderophore analogs are in planning.

[1] May, J. J., Wendrich, T. M., and Marahiel, M. A. (2001) J Biol Chem 276, 7209-7217
[2] May, J. J., Kessler, N., Marahiel, M. A., and Stubbs, M. T. (2002) Proc Natl Acad Sci U S A 99, 12120-12125
[3] Ollinger, J., Song, K.-B., Antelmann, H., Hecker, M., and Helmann, J. D. (2006) J Bacteriol 188, 3664-3673
[4] Marcus Miethke, M., Klotz, O., Linne, U., May, J. J., Beckering, C. L., and Marahiel, M. A. (2006), ms submitted for publication

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