Functional characterization of BbCRASP-2, a distinct outer membrane protein of Borrelia burgdorferi that binds host complement regulators factor H and FHL-1.
Borrelia burgdorferi, the aetiological agent of Lyme disease, employs sophisticated means to survive in diverse mammalian hosts. Recent studies demonstrated that acquisition of complement regulators factor H and factor H-like protein-1 (FHL-1) allows spirochetes to resist complement-mediated killing. Serum-resistant B. burgdorferi express up to five distinct complement regulator-acquiring surface proteins (CRASPs) that bind factor H and/or FHL-1. In this study we have identified and characterized one of those B. burgdorferi proteins, named BbCRASP-2. BbCRASP-2 is distinct from the four previously identified factor H/FHL-1-binding CRASPs of B. burgdorferi strains. The single copy of the gene encoding BbCRASP-2, cspZ, is located on the linear plasmid lp28-3. BbCRASP-2 is highly divergent from the factor H/FHL-1-binding protein BbCRASP-1 and from members of the factor H-binding Erp (OspE/F-related) protein family. Peptide mapping analysis revealed that the factor H/FHL-1 binding site is discontinuous and it was found that C-terminal truncations abrogate factor H and FHL-1 binding. The predominant BbCRASP-2 binding site of both host complement regulators was mapped to the short consensus repeat 7 (SCR 7). Factor H and FHL-1 bound to BbCRASP-2 maintain cofactor activity for factor I-mediated C3b inactivation and accelerate the decay of the C3 convertase. Expression of BbCRASP-2 in serum-sensitive B. burgdorferi mutant B313 increased resistance to complement-mediated lysis. The characterization of BbCRASP-2 now provides a complete picture of the three diverse complement regulator-binding protein families of B. burgdorferi yielding new insights into the pathogenesis of Lyme disease.
Hartmann
Kristina
K
Institute of Medical Microbiology, University Hospital of Frankfurt, Paul-Ehrlich-Str. 40, 60596 Frankfurt, Germany.
Corvey
Carsten
C
Skerka
Christine
C
Kirschfink
Michael
M
Karas
Michael
M
Brade
Volker
V
Miller
Jennifer C
JC
Stevenson
Brian
B
Wallich
Reinhard
R
Zipfel
Peter F
PF
Kraiczy
Peter
P
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D025065:Borrelia burgdorferi / Q000235:genetics / Q000378:metabolism*; D017242:Complement Factor H / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D008193:Lyme Disease / Q000097:blood / Q000276:immunology / Q000382:microbiology; D013058:Mass Spectrometry / Q000379:methods; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D011485:Protein Binding; D020349:Surface Plasmon Resonance / Q000379:methods
D001426:Bacterial Proteins; C486306:Fhl1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C440651:complement regulator-acquiring surface proteins, Borrelia burgdorferi; D017242:Complement Factor H