PMID: 10397151

 

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Title : Biochemical analysis and crystallisation of Fc gamma RIIa , the low affinity receptor for IgG

Abstract :

1. Fc gamma RIIa is one of a family of specific cell surface receptors for immunoglobulin
2. Fc gamma RIIa , which binds immune complexes of certain IgG isotypes, plays important roles in immune homeostasis
3. However, the precise characteristics of IgG binding and three-dimensional structure of Fc gamma RIIa have not been reported
4. This study describes the affinity of the Fc gamma RIIa : IgG interaction as well as biochemical characterisation of recombinant Fc gamma RIIa that has been used to generate high quality crystals
5. Equilibrium binding analysis of the Fc gamma RII:Ig G interaction found, IgG3 binds with an affinity of K(D) = 0.6 microM, as expected
6. Unlike other Fc gamma R, IgG4 also bound to Fc gamma RIIa , K(D) = 3 microM, clearly establishing Fc gamma RIIa as an IgG4 receptor
7. Biochemical analysis of mammalian and insect cell derived Fc gamma RIIa established the genuine N-terminus with Q being the first amino acid in the sequence Q, A, A, A, P.
9. extending the N-terminus further than previously thought
10. Furthermore, both potential N-linked glycosylation sites are occupied
11. Electrospray ionisation mass spectrometry (ESMS) indicate that the N-glycans of baculovirus derived Fc gamma RIIa are core mannose oligosaccharide side chains.
12. Finally, we describe the first crystallisation of diffraction quality crystals of soluble Fc gamma RIIa
13. Orthorhombic crystals diffract X-rays beyond 2.1 A resolution in the space group P 2(1 ) 2(1 )2 with cell dimensions a = 78.8 A, b = 100.5 A, c = 27.8 A
14. This marks a significant advance towards understanding the three-dimensional structure of Fc gamma RIIa and related FcR proteins that share high amino acid identity with Fc gamma RIIa