BBK32, a fibronectin binding MSCRAMM from Borrelia burgdorferi, contains a disordered region that undergoes a conformational change on ligand binding.
BBK32 is a fibronectin-binding lipoprotein on Borrelia burgdorferi, the causative agent of Lyme disease. Analysis using secondary structure prediction programs suggested that BBK32 is composed of two domains, an N-terminal segment lacking well defined secondary structure and a C-terminal segment composed largely of alpha-helices. Analysis of purified recombinant forms of the two domains by circular dichroism spectroscopy, gel permeation chromatography, and intrinsic viscosity determination were consistent with an N-terminal-extended, unstructured segment and a C-terminal globular domain in BBK32. Solid phase binding experiments suggest that the unstructured N-terminal domain binds fibronectin. Analysis of changes in circular dichroism spectra of the N-terminal segment of BBK32 upon binding of the N-terminal domain of fibronectin revealed an increase in beta-sheet content in the complex. Hence, BBK32, which belongs to a different family of proteins and shows no overall sequence similarity with the fibronectin binding MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) of Gram-positive bacteria, binds fibronectin by a mechanism that is reminiscent of the "tandem beta-zipper" previously demonstrated for the fibronectin binding of streptococcal adhesins.
Center for Extracellular Matrix Biology, Albert B. Alkek Institute of Biosciences and Technology, Texas A and M University System Health Science Center, Houston, Texas 77030, USA.
Jung Hwa
JH
Kim
Jenny
J
Singvall
Ulrich
U
Schwarz-Linek
Barbara J B
BJ
Johnson
Jennifer R
JR
Potts
Magnus
M
Höök
D018829:Adhesins, Bacterial / Q000378:metabolism; D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D015748:Borrelia burgdorferi Group / Q000737:chemistry*; D005353:Fibronectins / Q000378:metabolism*; D008024:Ligands; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D005353:Fibronectins; D008024:Ligands; C106209:p35 antigen, Borrelia