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Antibody Structure and Classes

Antibody Structure and Classes

Antibodies, also known as immunoglobulins, are produced by B cells in response to foreign substances, such as bacteria and viruses. These proteins are critical for recognizing and neutralizing these substances, protecting the body from potential harm.
The basic structure of an antibody consists of four protein chains: two identical heavy chains and two identical light chains. These chains are held together by disulfide bonds and other non-covalent interactions, forming a Y-shaped structure.

Antibody Structure

Antibody Structure

Overview
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.
The Y-Shaped Structure of Antibodies Consists of Four Polypeptide Chains
Antibodies consist of four polypeptide chains: two identical heavy...

Antibody Structure

Antibody Structure

Overview
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.
The Y-Shaped Structure of Antibodies Consists of Four Polypeptide Chains
Antibodies consist of four polypeptide chains: two identical heavy...

Gene Families

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Protein Complexes with Interchangeable Parts

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Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...

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The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...

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Related Experiment Video

Updated: Jul 15, 2026

A Scalable, Cell-Based Method for the Functional Assessment of Ube3a Variants

A Scalable, Cell-Based Method for the Functional Assessment of Ube3a Variants

Published on: October 10, 2022

Model structure of human APOBEC3G.

Kun-Lin Zhang¹, Bastien Mangeat, Millan Ortiz

¹Institute of Microbiology, University Hospital Center, University of Lausanne, Lausanne, Switzerland.

|April 19, 2007

Summary

A predicted 3D structure of apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) reveals key residues for viral packaging. This model aids in understanding APOBEC3G

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Area of Science:

Structural biology
Virology
Biochemistry

Background:

APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G) exhibits antiretroviral activity via viral DNA hypermutation.
APOBEC3G possesses two cytosine deaminase (CDA) domains; the N-CDA domain is catalytically inactive and contains the Vif interaction site.
No 3-D structure of APOBEC3G has been determined experimentally via X-ray crystallography or NMR.

Purpose of the Study:

To predict the 3-D structure of human APOBEC3G.
To identify key residues involved in APOBEC3G's interaction with Vif and its packaging into virions.
To guide further functional analysis of APOBEC3G.

Main Methods:

Homology modeling of APOBEC3G structure based on the crystal structure of APOBEC2.
Evaluation of 48 mutants within the APOBEC3G N-CDA domain.
Analysis of mutations affecting HIV-1 infectivity and APOBEC3G packaging.

Main Results:

A structural model of APOBEC3G was generated.
Key residue D128, important for Vif interaction, is surface-exposed with a negative electrostatic potential.
Residues R122 and W127 were identified as critical for APOBEC3G encapsidation and are located at the protein surface.

Conclusions:

The predicted APOBEC3G structure model highlights a cluster of residues essential for viral packaging.
This model provides a framework for future functional studies of APOBEC3G.
The findings contribute to understanding the mechanism of APOBEC3G's antiretroviral activity.