CRYSTALLIZATION STUDY OF THE IRON-REGULATED
PROTEIN FrpD FROM NEISSERIA MENINGITIDIS
Ekaterina Sviridova1, Ladislav Bumba2, Pavlina Rezacova3,4,
Peter Sebo2,5, Ivana Kuta Smatanova1,6
1Institute of Physical Biology USB CB, Zamek 136, 373 33 Nove Hrady, Czech Republic
2Institute of Microbiology AS CR, Videnska 1083, 142 20 Prague, Czech Republic
3Institute of Organic Chemistry and Biochemistry, Flemingovo nam. 2, 166 10 Prague, Czech Republic
4Insitute of Molecular Genetics AS CR Flemingovo nam. 2, 166 10 Prague, Czech Republic
5Institute of Biotechnology AS CR, Videnska 1083, 142 20 Prague, Czech Republic
6Institute of Systems Biology and Ecology AS CR, Zamek 136, 373 33 Nove Hrady, Czech Republic
Keywords: lipoprotein, iron-regulated protein
Introduction:
Neisseria meningitidis is a highly diverse
facultative bacterial pathogen. In most instances it colonizes its human host
without causing disease. Its occasional invasion, however, can entail
devastating diseases like septicemia or meningitis. Molecular basis of
meningococcal virulence remains difficult to analyze. However, several traits
potentially required for virulence of meningococci have been identified,
including presence of several iron acquisition systems.
Under conditions of limited iron availability, N.
meningitidis produces Fe-regulated
proteins, FrpD and FrpC, which both are encoded consecutively in an
iron-regulated frpDC operon
controlled by a ferric uptake regulator (Fur). FrpC belongs to a family of type
I-secreted RTX (Repeat in toxins) proteins and it may be
involved in the pathogenesis of meningococcal infection due to the presence of
high titers of anti-FrpC antibodies in convalescent-phase sera of a number of
patients after invasive meningococcal disease.
The iron-regulated protein FrpD was identified
as a N.
meningitidis outer membrane lipoprotein. FrpD is highly
conserved in a set of meningococcal strains and its primary amino acid sequence
does not exhibit any similarity to known protein sequences of other organisms.
The frpdD gene has the potential to encode two protein variants the
271-residue long FrpD sequence (FrpD271) and the 250-residue short
sequence (FrpD250). FrpD271 is synthesized
with a type II signal peptide for export across the cytoplasmic membrane. Then
it is posttranslationally modified by a lipid molecule and targeted to the
outer bacterial membrane. FrpD250 lacks the signal peptide and
possibly remains in the cytoplasm. The exported lipidated FrpD, as well as its
recombinant non-exported FrpD250 protein are both able to bind the
N-terminal portion of FrpC (within first 300 residues) with very high affinity
(apparent Kd=0.2 nM). FrpD may serve as an accessory
lipoprotein involved in anchoring of the secreted FrpC protein to the outer
bacterial membrane.
Results
and discussion:
This
project is aimed to determine the structure of FrpD protein and to perform the
structural characterization of FrpD. Our preliminary results showed the full version of FrpD250 protein
can not be crystallized. Therefore, we performed a specific truncation of 21
amino acid residues from N-terminus of FrpD250 protein. The
recombinant, truncated version (lacking the first 21 amino acid residues from
N-terminus) FrpD250 protein was expressed in non-methionine
auxotrophic Escherichia coli BL21λDE3 cultivated on the media
containing selenomethionine (Se-Met). Se-Met derived FrpD protein was purified
using a combination of metal affinity and gel-filtration chromatography. The crystals were obtained using a sitting drop vapour diffusion method.
Diffraction data were collected at the beamline MX BL14.1 of synchrotron BESSY (Berlin, Germany) at 100 K to the resolution of 2 Ǻ. The diffraction data
will be used to determine the structure of FrpD by single/multiple anomalous
diffraction (SAD/MAD) method.
References:
N.E. Rosenshtein, B.A. Perkins,
D.S. Stephens, T. Popovic, and J.M. Hughes, The New England Journal of
Medicine, 344, (2001), 1378-1388.
Y. L.Tzeng, D. S. Stephens, Microbes and Infection, 2, (2000), 687–700.
K. Prochazkova, R. Osicka, I. Linhartova, P. Halada, M. Sulc, and P. Sebo, The Journal of Biological Chemistry, 280, (2005), 3251-3258.
Acknowledgements
This project was
supported by grants MSM6007665808 and LC06010 (Ministry of Education of the
Czech Republic), AVOZ60870520 (Academy of Sciences of the Czech Republic) and
GACR 310/06/0720.