Abstract
Borrelia burgdorferi is a spirochete responsible for Lyme disease, the most commonly occurring vector-borne disease in Europe and North America. The bacterium utilizes a set of proteins, termed complement regulator-acquiring surface proteins (CRASPs), to aid evasion of the human complement system by recruiting and presenting complement regulator factor H on its surface in a manner that mimics host cells. Presented here is the atomic resolution structure of a member of this protein family, ErpC. The structure provides new insights into the mechanism of recruitment of factor H and other factor H-related proteins by acting as a molecular mimic of host glycosaminoglycans. It also describes the architecture of other CRASP proteins belonging to the OspE/F-related paralogous protein family and suggests that they have evolved to bind specific complement proteins, aiding survival of the bacterium in different hosts.
Highlights
Borrelia burgdorferi is a Gram-negative spirochete which, following transmission into the dermis during feeding of an infected Ixodes tick, may result in Lyme borreliosis, the most commonly occurring vectorborne disease in Europe and North America (Centers for Disease Control and Prevention, 2007; Steere, 1989; Steere et al, 2004)
The resistance of distinct Borrelia species towards the complement response upon exposure to human serum has been linked to the binding of the major alternative-pathway regulators factor H and factor-H-like protein-1 (FHL-1) by a family of molecules termed complement regulator-acquiring surface proteins (CRASPs; Kraiczy, Skerka, Brade et al, 2001; Kraiczy, Skerka, Kirschfink et al, 2001; Stevenson et al, 2002; Kraiczy & Stevenson, 2013)
ErpC is a member of the CRASP family of proteins which aid in complement evasion by B. burgdorferi by binding and presenting complement factor H on the bacterial cell surface under distinct circumstances (Kenedy & Akins, 2011)
Summary
Borrelia burgdorferi is a Gram-negative spirochete which, following transmission into the dermis during feeding of an infected Ixodes tick, may result in Lyme borreliosis, the most commonly occurring vectorborne disease in Europe and North America (Centers for Disease Control and Prevention, 2007; Steere, 1989; Steere et al, 2004). Following in vitro mutagenesis studies, a putative factor H binding site has been proposed within the cleft between the two subunits which interacts with factor H and FHL-1 in the region of domains 5–7 (Kraiczy et al, 2004, 2009). Another member of the CRASP family, ErpC ( referred to as BbCRASP-4), is an 18 kDa protein that belongs to the OspE/F-related (Erp) paralogous family of proteins and has been demonstrated to bind factor H (Kraiczy, Skerka, Brade et al, 2001; Kenedy & Akins, 2011).
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