Integrated structural biology study of the FrpD protein from Neisseria meningitidis

E. Sviridova1,2, L. Bumba3, P. Rezacova4,5, V. Veverka4, G. Schenk6, P. Sebo3,7 and  I. Kuta Smatanova1,2

1Faculty of Science USB CB, Branišovska 1760, 37005 Ceske Budejovice, Czech Republic

2Institute of Microbiology AS CR, Zamek 136, 37333 Nove Hrady, Czech Republic

3Institute of Microbiology AS CR, Videnska 1083, 14220 Prague, Czech Republic

4Institute of Organic Chemistry and Biochemistry AS CR, Flemingovo nam. 2, 16610 Prague, Czech Republic

5Institute of Molecular Genetics AS CR Flemingovo nam. 2, 16610 Prague, Czech Republic

6EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany

7Institute of Biotechnology AS CR, Videnska 1083, 14220 Prague, Czech Republic

eesviridova@gmail.com

FrpD is a highly conserved lipoprotein of Neisseria meningitidis anchored to the bacterial outer membrane. The frpD gene sequence contains two translation initiation sites, which give rise to production of the full-length FrpD protein (FrpD271) that harbours N-terminal signal peptide promoting FrpD export across the cytoplasmic membrane by Sec translocase, and the truncated FrpD protein (FrpD250) that lacks the signal peptide and remaining in cytoplasm of the bacteria. The exported FrpD271 precursor is processed to its mature form on the periplasmic side of the cytoplasmic membrane, sequentially modified by a lipid molecule at Cys25 residue, and sorted to the outer bacterial membrane [1]. The biological function of FrpD is unknown. It appears to be linked to the FrpC protein, since FrpD was found to bind the N-terminal part of FrpC with very high affinity (Kd = 0.2 nM) [1]. However, mechanism of FrpD-FrpC interaction is unknown due to the absence of structural information on these proteins.

We present here the first crystal and solution structures of the FrpD protein and the NMR spectroscopy identification of the FrpD-FrpC interaction interface. According to the detailed structure analysis, the atomic structures of FrpD reveal a novel protein fold. Our work constitutes the first step in clarifying the molecular basis of FrpD-FrpC interaction and sets the base for further investigation of the role of FrpD in the virulence mechanism of N. meningitidis and for the functional and biochemical characterization of the high affinity interaction between the FrpD protein and the FrpC protein.

1. K. Prochazkova, R. Osicka, I. Linhartova, P. Halada, M. Sulc, and P. Sebo, J. Biol. Chem., 280, (2005), 3251-3258.

This research was supported by the GACR (P207/11/0717).