Name: antibody heavy and light chains
Uploaded: 2020-11-23T11:47:34.000Z
Duration: 1 min 10 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

BIO1.LS1.3

Antibody Structure

Antibodies also known as immunoglobulins are key players in the humoral immune response against foreign antigens.
They are proteins that consist of four polypeptides in a Y-shape structure. With two identical heavy and two identical light chains. Linked together through a combination of noncovalent bonds and covalent disulfide bonds.
At the very tips of each polypeptide chain are unique variable domains that selectively bind antigens. While some parts of this region interact directly, other parts provide structural support for these binding sites.
In contrast, the stem region of the antibody, known as the constant region, determines the specific immunological mechanism of action depending on the class.
For instance, one type, Immunoglobulin E, is secreted in the body in response to an allergen, like cat dander, and mediates the allergic reaction.

antibody structure

<h4>Overview</h4>
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.
<h4>The Y-Shaped Structure of Antibodies Consists of Four Polypeptide Chains</h4>
Antibodies consist of four polypeptide chains: two identical heavy chains of approximately 440 amino acids each, and two identical light chains composed of roughly 220 amino acids each. These chains are arranged in a Y-shaped structure that is held together by a combination of covalent disulfide bonds and noncovalent bonds. Furthermore, most antibodies carry sugar residues. The process of adding sugar side chains to a protein is called glycosylation.
<h4>The Subunits of an Antibody Have Different Functions</h4>
Both the light chain and heavy chain contribute to the antigen binding site at each of the tips of the Y structure. These 110-130 amino acids are highly variable to allow recognition of an almost unlimited number of antigens. This region is also called the variable region and is part of the antigen binding fragment.
Each arm of the Y-shaped unit carries an identical antigen binding site. Antibodies can crosslink antigens: when one arm binds to one antigen and the other arm binds to a second, structurally identical antigen. Crosslinking is facilitated by the flexible hinge region that connects the antibody&rsquo;s arms to the stem and allows variable distances between antigen binding sites. Large lattices of crosslinked antigens are subsequently engulfed more quickly and easily by macrophages, removing larger amounts of the antigen at once.
The stem region of the antibody is also called the fragment crystallizable (Fc) region and determines the effector function of the antibody. Via the Fc domain, the antibody can interact with Fc receptors on other immune cells, such as B cells, macrophages, and mast cells. The Fc region is often glycosylated, hindering or allowing Fc receptor access. Altering the glycosylation state of the antibody, therefore, allows rapid modulation of antibody function.
<h4>Mammals Have Five Classes of Antibodies</h4>
Antibodies are classified by their number of Y-shaped structures and type of heavy chains. Antibodies of the class IgD, IgE and IgG have a single Y-shaped structure, providing two identical antigen binding sites at the tips of their arms. In more scientific terms: they have a valency of two. IgD, IgE, and IgG differ, however, in the composition of disulfide and noncovalent bonds between their two heavy chains. IgA can occur as a monomer or as a dimer, resembling two Ys that are joined at their base. As a dimer, IgA has four identical antigen binding sites&mdash;a valency of four. IgM can occur as a monomer but is more often encountered as a pentamer, giving it a valency of 10.
<h4>The Five Classes of Antibodies Trigger Different Immune Functions</h4>
IgG antibodies are the most abundant antibody molecules in blood and are secreted in large volumes when a specific pathogen is encountered for the second time. IgGs contribute to pathogen elimination in several ways. They opsonize pathogens to trigger phagocytosis by macrophages or neutrophils. The activity of these phagocytic cells is enhanced by the complement system, a cascade of enzymatic proteins. The complement system is itself triggered by IgG. Furthermore, IgGs are the only antibodies that can cross the placenta from the mother to the fetus. They are also secreted into the mother&rsquo;s milk, thereby offering passive immunity that protects the infant from infections.
IgA protects mucosal surfaces such as the gastrointestinal, respiratory, and urogenital tracts. It foremost neutralizes bacteria, preventing their movement across epithelia. IgA is also secreted into mucus, tears, saliva, and colostrum (the antibody-rich secretion of a mother&rsquo;s breast for the first days after giving birth). IgA occurs as a dimer when it is secreted and as a monomer in body fluids.
Monomers of the IgM class are the first to appear on naive B cells. IgMs are the major class of antibodies that are secreted by B cells in response to the first exposure to an antigen&mdash;the primary antibody response. When an antigen binds to an IgM molecule, it activates the complement system and neutralizes pathogens.
The functions of IgD antibodies are not well understood but seem to resemble those of IgM.
IgE is challenging to study due to their low levels in body fluids and are mostly known for their negative impact on human well-being: allergies. During an allergic reaction, IgE binds to its cognate antigen. Subsequently, the Fc region of IgE binds to mast cells and basophils, a type of white blood cell. The interaction of IgE and the Fc-receptor on the cell surface elicits the release of histamines and interleukins, which in turn causes allergic symptoms such as sneezing and itching.
<h4>Antibodies for Research, Diagnostic and Therapeutics Are Produced in Animals</h4>
Antibodies are an important tool in many research disciplines as well as in the diagnosis, and sometimes treatment of disease. To produce antibodies, an antigen is injected into a farm or laboratory animal, often rabbits, chickens, hamsters, or goats, and is later isolated from the animal&rsquo;s blood.

Overview
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced ...

Education

JoVE Core

Molecular Biology

Unit 1

Protein Structure

KEY TERMS AND CONCEPTS

antibody heavy and light chains

Antibodies are built from heavy and light chains that work together to form a Y-shaped molecule. These chains give the antibody its basic structure and help it bind to specific targets.

The two upper arms of the Y contain the variable regions, which differ from one antibody to another. These variable regions help determine which antigen, or foreign molecule, the antibody can recognize.

The lower part of the antibody is the constant region. This region is more similar across antibodies and helps define the antibody class. The structure of the chains also supports the antibody’s overall shape and function.

Antibody Heavy and Light Chains

what are proteins?

Proteins, Amino Acids, and Polypeptides

Proteins are built from amino acids and form polypeptides. Amino acids are the small building blocks, and a polypeptide is a chain of amino acids joined together. This basic relationship explains how proteins are made and why their structure matters. Proteins have several important roles in living things. Some proteins help build body structures, while others carry out work inside cells. The transcript also connects proteins to enzymes, which are proteins that speed up chemical reactions.

protein organization

Protein Organization and Folding Levels

Protein organization describes how a protein is arranged at several levels. These levels help explain how a chain of amino acids becomes a working molecule. The main stages are primary, secondary, tertiary, and quaternary structure. Primary structure is the linear order of amino acids in the protein chain. Secondary structure is the first step of folding. In this stage, the chain can form patterns such as helices and sheets. Tertiary structure is the overall three-dimensional shape of one...

protein folding

Protein Folding and Structure

Protein folding is the process that gives a protein its final three-dimensional shape. That shape is essential because a protein’s structure helps determine how it works in the cell. A folded protein is stabilized by several interactions. These include hydrogen bonds, van der Waals interactions, and disulfide bridges. Each one helps hold the protein in the correct form. When a protein does not fold properly, its structure can change. That can affect its function and can interfere with normal...

conservation of protein domains over different proteins

conservation-of-protein-domains-over-different-proteins

Argonaute Protein Domains Across Species

Argonaute proteins have conserved domains that help small RNAs guide gene silencing. These proteins are found across organisms, but the number of Argonaute family members can differ from one species to another. Protein domains are small, structurally independent parts of a single amino acid chain. They can keep their shape on their own, but they may still work together with other parts of the protein. During evolution, domains can duplicate, recombine, and form new combinations. This process,...

globular and fibrous proteins

Protein Shapes: Globular vs Fibrous

Proteins can be grouped by shape into globular proteins and fibrous proteins. These two subtypes also differ in how they dissolve in water and in the jobs they do in cells and tissues. Globular proteins, also called spheroproteins, are usually round in shape. They contain a mix of amino acid types and varied primary sequences. Their shapes support many functions, including enzymes, cellular messengers, and molecular transporters. These roles often need the proteins to stay soluble in the...

intrinsically disordered proteins

Flexible Protein Regions and Binding

Intrinsically disordered proteins are proteins that do not fold into one fixed three-dimensional shape. Their flexible structure helps them work with ordered proteins to do jobs that rigid proteins cannot easily do. They are found more often in eukaryotes than in prokaryotes, and they can be fully disordered or made of both ordered and disordered regions. This lack of a rigid shape is linked to amino acid makeup. These proteins usually have many polar and charged amino acids and fewer...

protein complex assembly

How Proteins Self-Assemble in Cells

Proteins can self-assemble into working complexes inside cells. Some complexes are homomeric, which means they contain more than one copy of the same protein. Others are heteromeric, which means they are built from different protein types. Most protein complexes form through ordered self-assembly. In some cases, assembly factors help guide the proteins into the correct structure. Even in the crowded space inside a cell, proteins usually find the right partners and form functional complexes. <br...

conjugated proteins

Conjugated Proteins and Their Roles

Conjugated proteins are proteins that bond with a non-protein part. Unlike simple proteins, which contain only amino acids, these protein complexes include another chemical moiety attached covalently. That extra part can change how the protein works in the body. Nucleoproteins are conjugated proteins that contain nucleic acids. They are grouped as deoxyribonucleoproteins (DNPs) or ribonucleoproteins (RNPs). A nucleosome is a common DNP example, where nuclear DNA is associated with histone...

amyloid fibrils

Amyloid Fibrils in Brain Disease

Amyloid fibrils are clumps of misfolded proteins linked to brain disease and other disorders. In normal cells, misfolded proteins are usually refolded by chaperone proteins or broken down by the proteasome. But in some mutations or diseases, these proteins can build up into large clusters and then assemble into long fibers called fibrils. Amyloid deposits were seen as early as 1639 in the liver and spleen. In 1854, Rudolph Virchow used iodine staining, a method normally used to identify...

Antibodies are built from heavy and light chains that work together to form a Y-shaped molecule. These chains give the antibody its basic structure and help it bind to specific targets. The two upper arms of the Y contain the variable regions, which differ from one antibody to another. These variable regions help determine which antigen, or foreign molecule, the antibody can recognize. The lower part of the antibody is the constant region. This region is more similar across antibodies and...

protein families

Protein Families and Superfamilies

Protein families are groups of homologous proteins with similar amino acid sequences and three-dimensional shapes. They often appear after gene duplication, when an extra copy of a gene is added to an organism’s genome. Mutations can then change the amino acids, as long as the protein can still be made correctly. If the new proteins keep similar amino acids in key places, their domains and overall three-dimensional structure can stay similar too. Members of the same family can share as little...

key terms and concepts

Explore how antibody heavy and light chains form a Y-shaped molecule, with variable regions for target binding and a constant region that helps define class.

Antibody Heavy and Light Chains | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

Arizona Science Standards

Life Science

HS+B.L1

HS+B.L1U1.5

myJoVE Corporation

Characteristics of Life

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the-tree-of-life-bacteria-archaea-and-eukaryotes

The Tree of Life - Bacteria, Archaea, and Eukaryotes

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Compare and contrast existing models, identify patterns, and use structural and functional evidence to analyze the characteristics of life. Engage in argument about the designation of viruses as non-living based on these characteristics.
EXPLANATION: Students begin to develop patterns of living and non-living organisms in kindergarten and build on detailed characteristics of different classifications of living organisms throughout elementary and middle school. Biology 1 discussions introduce viral particles and viral cycles, building on student understanding of living organisms to engage in an argument regarding the classification of a viral particle as either living or non-living.

BIO1.LS1.1

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BIO1.LS1.2

Nucleic Acids

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DNA Packaging

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Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside ...

Organization of Genes

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Replication in Eukaryotes

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Mutations

Overview

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. ...

Transcription

Overview
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Translation

Lesson: Translation
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Types of RNA

Overview
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MicroRNAs

siRNA - Small Interfering RNAs

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piRNA - Piwi-interacting RNAs

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CRISPR and crRNAs

Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect ...

lncRNA - Long Non-coding RNAs

In humans, more than 80% of the genome gets transcribed. However, only around 2% of the genome codes for proteins. The remaining part produces non-coding ...

What are Proteins?

Protein Organization

Protein Folding

Protein Families

Protein families are groups of homologous proteins; that is, they have similarities in amino acid sequences and three-dimensional structures. Protein ...

Conservation of Protein Domains Over Different Proteins

Protein domains are small structurally independent units that are part of a single amino acid chain.&#160; Although these domains are often structurally ...

Globular and Fibrous Proteins

Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
Globular ...

Intrinsically Disordered Proteins

Intrinsically disordered proteins are a group of proteins that do not fold into specific three-dimensional structures. Their structural flexibility allows ...

Protein Complex Assembly

Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.&#160; Most protein complexes ...

Conjugated Proteins

Simple proteins and protein complexes contain only amino acids. In contrast, many other proteins, called conjugated proteins, covalently bond with ...

Allosteric Proteins-ATCase

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Amyloid Fibrils

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Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand ...

Phosphorylation

Ligand Binding Sites

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Protein Kinases and Phosphatases

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Protein-protein Interfaces

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GTPases and their Regulation

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Conserved Binding Sites

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Covalently Linked Protein Regulators

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the-equilibrium-binding-constant-and-binding-strength

The Equilibrium Binding Constant and Binding Strength

The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at ...

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

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Cofactors and Coenzymes

Mechanical Protein Functions

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Allosteric Regulation

Structural Protein Function

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Ligand Binding and Linkage

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Protein Networks

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Integrate evidence to develop a structural model of a DNA molecule. Using the model, develop and communicate an explanation for how DNA serves as a template for self-replication and encodes biological information.
EXPLANATION: Discussions of DNA in earlier grades have been limited to discussions of genes and the role of genes in the appearance and activities of an organism. Biology 1 represents a student's introduction to a molecular model of a DNA as well as the organization of DNA into genes and genes subsequently into chromosomes. Students should address interactions between genes in proteins which regulate both the shape and reproduction of DNA molecules. It is important to note that not all segments of DNA are transcribed for proteins. Portions of DNA are involved in regulating the expression of genes or affect the structure of the chromosomes (replication origin, centromeres, and telomeres).

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The Cell Cycle Control System

Positive Regulator Molecules

Inhibition of CDK Activity

S-Cdk Initiates DNA Replication

M-Cdk Drives Transition Into Mitosis

Mitogens and the Cell Cycle

Replicative Cell Senescence

Abnormal Proliferation

cells-coordinate-growth-and-proliferation

Cells Coordinate Growth and Proliferation

Mitosis and Cytokinesis

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Chromosome Duplication

Cohesins

Condensins

The Mitotic Spindle

Centrosome Duplication

Create a model for the major events of the eukaryotic cell cycle, including mitosis. Compare and contrast the rates of cell division in various eukaryotic cell types in multicellular organisms.
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BIO1.LS1.6

Antibody Heavy and Light Chains

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