Antibody- Structure, Classes and Functions
Antibody molecules have a common structure of four peptide chains. This structure consists of two identical light (L) chain polypeptide of about. In this lesson, we will explore your immune system and how it deals with invaders , such as microbes and bacteria. We will define antibodies and discuss their. Antigen binding by antibodies is the primary function of antibodies and can result very useful in elucidating structure/function relationships in immunoglobulins. . The term opsonin is used to describe substances that enhance phagocytosis.
Fundamentals of Antibody Structure & Function - Maine Biotechnology
In this view, the HV regions of the Fab have been deleted. The FR regions of the antibody do not contact the antigen. This ribbon structure shows the antibody's HV purple and FR yellow regions of the Fab, and their interaction with an epitope of the antigen. In hen egg white lysozyme, a glutamine at position Gln protrudes away from the antigen surface. In this view, Gln is circled. The antibody is not shown.
The following images show how this feature is important for the formation of a high affinity antibody-antigen interactions. The antibody's HV region forms an opening to surround the antigen's protruding Gln green.
Hydrogen bonds yellow stabilize the antibody-antigen interaction. In addition to hydrogen bonds, other weak interactions such as van der Waals forces, hydrophobic interactions and electrostatic forces improve the binding specificity between antibody and antigen. Half-life is about 23 days. IgG is the only antibody that can cross placenta. It cross placenta and provide immunity to fetus upto 6 month of age. The immunity is known as natural passive immunity. It can also activate complement.
IgG is the major antibody produced in secondary immune response. Ig, IgG3 and IgG4 readily cross the placenta and play important role in protecting the fetus. IgG4 is not able to activate complement at all. IgG1 and IgG3 binds with high affinity to Fc receptor on phagocytic cell and thus mediate opsonization.
IgG helps in bacterial immobilization.Antibody structure and function
The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field Figure 1. Antigen binding Immunoglobulins bind specifically to one or a few closely related antigens. Each immunoglobulin actually binds to a specific antigenic determinant.
Describe how the structure of an antibody is related to its function? | MyTutor
Antigen binding by antibodies is the primary function of antibodies and can result in protection of the host. The valency of antibody refers to the number of antigenic determinants that an individual antibody molecule can bind.
- Describe how the structure of an antibody is related to its function?
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- Antibody: Structure, classes and functions
The valency of all antibodies is at least two and in some instances more. Effector Functions Frequently the binding of an antibody to an antigen has no direct biological effect.
Rather, the significant biological effects are a consequence of secondary "effector functions" of antibodies. The immunoglobulins mediate a variety of these effector functions.
Antibody- Structure, Classes and Functions
Usually the ability to carry out a particular effector function requires that the antibody bind to its antigen. Not every immunoglobulin will mediate all effector functions. Such effector functions include: Fixation of complement - This results in lysis of cells and release of biologically active molecules see chapter two 2. Binding to various cell types - Phagocytic cells, lymphocytes, platelets, mast cells, and basophils have receptors that bind immunoglobulins. This binding can activate the cells to perform some function.
Some immunoglobulins also bind to receptors on placental trophoblasts, which results in transfer of the immunoglobulin across the placenta. As a result, the transferred maternal antibodies provide immunity to the fetus and newborn III.
Although different immunoglobulins can differ structurally, they all are built from the same basic units. Heavy and Light Chains All immunoglobulins have a four chain structure as their basic unit. They are composed of two identical light chains 23kD and two identical heavy chains kD B. Inter-chain disulfide bonds - The heavy and light chains and the two heavy chains are held together by inter-chain disulfide bonds and by non-covalent interactions The number of inter-chain disulfide bonds varies among different immunoglobulin molecules.
Intra-chain disulfide binds - Within each of the polypeptide chains there are also intra-chain disulfide bonds. Variable V and Constant C Regions When the amino acid sequences of many different heavy chains and light chains were compared, it became clear that both the heavy and light chain could be divided into two regions based on variability in the amino acid sequences.