Research Article: Structures of the rat complement regulator CrrY

Date Published: July 1, 2011

Publisher: International Union of Crystallography

Author(s): Pietro Roversi, Steven Johnson, Joseph J. E. Caesar, Florence McLean, Kirstin J. Leath, Stefanos A. Tsiftsoglou, B. Paul Morgan, Claire L. Harris, Robert B. Sim, Susan M. Lea.

http://doi.org/10.1107/S1744309111016551

Abstract

The structure of rat CrrY1–4 determined in two distinct crystal forms shows a pronounced bend at the interface between domains 3 and 4.

Partial Text

Complement constitutes the most ancient arm of the immune system, providing a first line of defence against blood infection by pathogens, and links innate to cellular immunity (Ricklin et al., 2010 ▶). Prevention of activation on self-surfaces is achieved by complement regulatory proteins (Liszewski et al., 1996 ▶). The two main complement regulation mechanisms that protect self-tissue from unwanted complement activation are decay-acceleration activity (DAA), in which the regulator dissociates the complement-activating C3 and C4 convertases, and factor I cofactor activity (CA), in which the regulator assists the serine protease factor I in cleaving and degrading the same C3 and C4 convertase precursors, C4b and C3b (Walport, 2001a ▶,b ▶).

The two crystal structures of rat CrrY1–4 show a hockey-stick-shaped molecule with the elongated handle comprising CCP domains 1–3, with approximate dimensions 25 × 25 × 120 Å, and the blade made by CCP domain 4 (Fig. 1 ▶a). The electron density of the crystal form diffracting to 2.5 Å resolution allowed unambiguous tracing of residues 37–290 (Fig. 1 ▶b). The loop 52–54 is poorly ordered in the lower resolution structure. The domains are standard CCP domains and are organized in β-­sheets held together by two disulfide bridges (Fig. 2 ▶a).

 

Source:

http://doi.org/10.1107/S1744309111016551

 

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