Interaction of the globular domain of human C1q with Salmonella typhimurium lipopolysaccharide.
Gram-negative bacteria can bind complement protein C1q in an antibody-independent manner and activate classical pathway via their lipopolysaccharides (LPS). Earlier studies have implicated the collagen-like region of human C1q in binding LPS. In recent years, a number of C1q target molecules, previously considered to interact with collagen-like region of C1q, have been shown to bind via the globular domain (gC1q). Here we report, using recombinant forms of the globular head regions of C1q A, B and C chains, that LPS derived from Salmonella typhimurium interact specifically with the B-chain of the gC1q domain in a calcium-dependent manner. LPS and IgG-binding sites on the gC1q domain appear to be overlapping and this interaction can be inhibited by a synthetic C1q inhibitor, suggesting common interacting mechanisms.
Roumenina
Lubka T
LT
Department of Biochemistry, Sofia University, St. Kliment Ohridski, 8 Dragan Tsankov St., Sofia 1164, Bulgaria.
Popov
Krustyo T
KT
Bureeva
Svetlana V
SV
Kojouharova
Mihaela
M
Gadjeva
Mihaela
M
Rabheru
Shweta
S
Thakrar
Roshni
R
Kaplun
Alexander
A
Kishore
Uday
U
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D003167:Complement Activation; D015922:Complement C1q / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000737:chemistry / Q000276:immunology; D014315:Triterpenes / Q000494:pharmacology; D000094062:Betulinic Acid
D002118:Calcium; D015922:Complement C1q; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D011993:Recombinant Fusion Proteins; D014315:Triterpenes; C002503:betulin; D000094062:Betulinic Acid