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Mapping the active site of CD59
1Department of Pathology, New York University Medical Center, New York 10016, USA.
Abstract:
CD59 is a widely distributed membrane-bound inhibitor of the cytolytic membrane attack complex (MAC) of complement. This small (77 amino acid) glycoprotein is a member of the Ly6 superfamily of proteins and is important in protecting host cells from the lytic and proinflammatory activity of the MAC. CD59 functions by binding to C8 and/or C9 in the nascent MAC and interfering with C9 membrane insertion and polymerization. We present data obtained from a combination of molecular modeling and mutagenesis techniques, which together indicate that the active site of CD59 is located in the vicinity of a hydrophobic groove on the face of the molecule opposite to a "hydrophobic strip" suggested earlier. In addition, removal of the single N-linked glycosylation site at Asn18 of CD59 resulted in an enhancement of complement inhibitory activity.
Insights
CD59 protein inhibits the membrane attack complex (MAC) of complement. Molecular modeling and mutagenesis reveal CD59
Area of Science:
- Immunology
- Molecular Biology
- Structural Biology
Background:
- CD59 is a crucial complement inhibitor protecting host cells from MAC-mediated damage.
- It belongs to the Ly6 superfamily and regulates complement's lytic and inflammatory functions.
Purpose of the Study:
- To elucidate the active site of CD59 using molecular modeling and mutagenesis.
- To investigate the role of glycosylation in CD59's complement inhibitory activity.
Main Methods:
- Molecular modeling techniques were employed to analyze CD59 structure.
- Site-directed mutagenesis was used to identify key residues and functional sites.
- Complement inhibitory activity was assessed after modifying the glycosylation site.
Main Results:
- The active site of CD59 is localized near a hydrophobic groove, distinct from previously proposed regions.
- Removal of the N-linked glycosylation site at Asn18 enhanced CD59's complement inhibitory function.
- Mutagenesis data refined the understanding of CD59's interaction with C8 and C9.
Conclusions:
- The study precisely maps the CD59 active site, advancing our understanding of complement regulation.
- Glycosylation at Asn18 negatively impacts CD59's inhibitory efficacy.
- These findings offer insights for developing targeted therapies involving the complement system.