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Infection and Immunity, December 2001, p. 7501-7511, Vol. 69, No. 12
Graduate School of Biomedical Sciences and
Department of Pathology and Laboratory Medicine, Medical
School, University of Texas Health Science Center at Houston, Houston,
Texas 77030
Received 10 April 2001/Returned for modification 26 June
2001/Accepted 31 August 2001
Mycobacterium tuberculosis and Mycobacterium
avium are facultative intracellular pathogens that are able to
survive and replicate in mononuclear phagocytes. Human complement
component C3 has previously been shown to mediate attachment and
phagocytosis of these bacteria by mononuclear phagocytes. In this
study, a C3 ligand affinity blot protocol was used to identify a 30-kDa
C3-binding protein in M. tuberculosis and
Mycobacterium smegmatis and a 31-kDa C3-binding protein in
M. avium. The C3-binding proteins in M. tuberculosis and M. avium localized to the cell
membrane fraction and partitioned to the detergent fraction during
Triton X-114 phase partitioning. The C3-binding protein from M. tuberculosis was partially purified using a cation exchange
column and was shown to bind concanavalin A. The N terminus and an
internal fragment of the partially purified C3-binding protein were
subjected to amino acid sequence analysis. The resulting amino acid
sequences matched the M. tuberculosis heparin-binding
hemagglutinin (HbhA) protein. Recombinant full-length HbhA and the C
terminus of HbhA fused to maltose-binding protein, but not recombinant
HbhA lacking the C-terminal region, bound human C3. Recombinant
full-length HbhA coated on polystyrene beads, was found to enhance the
adherence and/or phagocytosis of the coated beads to J774.A1 cells in
both the presence and absence of human serum. The presence of
complement-sufficient serum increased the adherence of the HbhA-coated
beads to the J774.A1 cells in a C3-dependent manner. If HbhA within the
bacterial cell membrane functions similarly to isolated HbhA, this
protein may enhance the adherence and phagocytosis of M. tuberculosis and M. avium to mononuclear phagocytes
through the binding of C3 and interaction with C3 receptors on
mononuclear phagocytes.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.12.7501-7511.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Mycobacterial Protein HbhA Binds Human Complement Component
C3
*
Corresponding author. Mailing address: Department of
Pathology and Laboratory Medicine, University of Texas Medical School, P.O. Box 20708, Houston, TX 77225. Phone: (713) 500-5338. Fax: (713)
500-0730. E-mail: Steven.J.Norris{at}uth.tmc.edu.
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