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Purification and Aggregation of the Amyloid Precursor Protein Intracellular Domain
Published on: August 28, 2012
The APOBEC-2 crystal structure and functional implications for the deaminase AID
Courtney Prochnow1, Ronda Bransteitter, Michael G Klein
1Molecular and Computational Biology, University of Southern California Los Angeles, California 90089, USA.
The crystal structure of apolipoprotein B messenger RNA-editing enzyme catalytic polypeptide 2 (APOBEC-2) reveals a unique rod-shaped tetramer. This structure provides insights into how mutations in related proteins, like activation-induced cytidine deaminase, can impair antibody maturation.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- APOBEC-2 (APO2) is part of the APOBEC family, known for deaminating mRNA and single-stranded DNA.
- APOBEC proteins perform diverse biological functions, including antibody generation (AID) and antiviral defense (APOBEC-3).
Purpose of the Study:
- To determine the crystal structure of APOBEC-2 (APO2).
- To understand the structural basis of APO2's tetrameric formation and its implications for APOBEC family function.
Main Methods:
- X-ray crystallography to determine the APO2 structure.
- Structure-based predictions were tested on activation-induced cytidine deaminase (AID) due to sequence homology.
Main Results:
- APO2 forms a distinct rod-shaped tetramer, differing from the square-shaped tetramer of cytidine deaminase.
- The APO2 monomer structure, with two long alpha-helices, facilitates head-to-head dimer interactions to form the rod-shaped tetramer.
- Mutations affecting AID's oligomerization and substrate access, predicted from the APO2 structure, impaired its deamination activity.
Conclusions:
- The APO2 structure reveals a novel tetrameric assembly mechanism within the APOBEC family.
- Understanding APO2's structure provides a framework for interpreting how mutations in AID lead to hyper-IgM-2 syndrome and defective antibody maturation.
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