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Protein-protein recognition: The neonatal Fe receptor and immunoglobulin G

Citation

Martin, Warham Lance (2001) Protein-protein recognition: The neonatal Fe receptor and immunoglobulin G. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9ek6-6833. https://resolver.caltech.edu/CaltechTHESIS:03072014-143524462

Abstract

The neonatal Fe receptor (FeRn) binds the Fe portion of immunoglobulin G (IgG) at the acidic pH of endosomes or the gut and releases IgG at the alkaline pH of blood. FeRn is responsible for the maternofetal transfer of IgG and for rescuing endocytosed IgG from a default degradative pathway. We investigated how FeRn interacts with IgG by constructing a heterodimeric form of the Fe (hdFc) that contains one FeRn binding site. This molecule was used to characterize the interaction between one FeRn molecule and one Fe and to determine under what conditions FeRn forms a dimer. The hdFc binds one FeRn molecule at pH 6.0 with a K_d of 80 nM. In solution and with FeRn anchored to solid supports, the heterodimeric Fe does not induce a dimer of FeRn molecules. FcRnhdFc complex crystals were obtained and the complex structure was solved to 2.8 Å resolution. Analysis of this structure refined the understanding of the mechanism of the pH-dependent binding, shed light on the role played by carbohydrates in the Fe binding, and provided insights on how to design therapeutic IgG antibodies with longer serum half-lives. The FcRn-hdFc complex in the crystal did not contain the FeRn dimer. To characterize the tendency of FeRn to form a dimer in a membrane we analyzed the tendency of the hdFc to induce cross-phosphorylation of FeRn-tyrosine kinase chimeras. We also constructed FeRn-cyan and FeRn-yellow fluorescent proteins and have analyzed the tendency of these molecules to exhibit fluorescence resonance energy transfer. As of now, neither of these analyses have lead to conclusive results. In the process of acquiring the context to appreciate the structure of the FcRn-hdFc interface, we developed a study of 171 other nonobligate protein-protein interfaces that includes an original principal component analysis of the quantifiable aspects of these interfaces.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Biochemistry and Molecular Biophysics
Degree Grantor:California Institute of Technology
Division:Biology
Major Option:Biochemistry and Molecular Biophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bjorkman, Pamela J.
Thesis Committee:
  • Unknown, Unknown
Defense Date:17 May 2001
Record Number:CaltechTHESIS:03072014-143524462
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:03072014-143524462
DOI:10.7907/9ek6-6833
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8116
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:07 Mar 2014 23:56
Last Modified:16 Apr 2021 22:29

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