Name: how amino acid sequence shapes proteins
Uploaded: 2023-04-30T10:34:15.000Z
Duration: 1 min 25 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Protein Folding

En un péptido recién sintetizado, las interacciones entre sus aminoácidos constituyentes guían su plegamiento en una estructura tridimensional estable llamada conformación nativa, a menudo su forma funcional.
En primer lugar, la cadena polipeptídica lineal se pliega en alfa-hélices y beta-láminas a través de enlaces de hidrógeno entre residuos de aminoácidos.
Las cadenas laterales hidrofóbicas que sobresalen de las hélices o láminas beta se unen, eliminando las moléculas de agua circundantes. Como resultado, el polipéptido se empaqueta en un intermedio ligeramente plegado con un núcleo hidrofóbico.
Los residuos polares en la superficie forman enlaces de hidrógeno adicionales e interacciones iónicas, mientras que las cisteínas adyacentes forman enlaces disulfuro covalentes para estabilizar la proteína en su conformación nativa.
En el caso de las proteínas con múltiples cisteínas, la enzima isomerasa disulfuro cataliza el intercambio rápido de grupos tiol, lo que permite la correcta formación de enlaces disulfuro.
La mayoría de las proteínas no se pliegan por sí mismas y son ayudadas por las proteínas de choque térmico y las chaperoninas.
Estas chaperonas moleculares aceleran el proceso de plegamiento al unirse al péptido desplegado y evitar la agregación o proporcionar un microambiente donde el péptido puede plegarse en su conformación nativa.

<ol>
	<li>Lodish, Harvey, et al. Biología celular molecular. 8ª ed. W.H. Freeman and Company, 2016. Págs. 81-85</li>
	<li>Donald Voet y Judith G Voet Bioquímica. 4ª ed. JOHN WILEY & SONS, INC. 2011. págs. 278-290</li>
	<li>Nelson y Cox, Lehninger, Principios de bioquímica, 7ª ed. W.H. Freeman and Company, 2016. págs. 396-407</li>
</ol>

plegado de proteínas

Las proteínas son cadenas de aminoácidos unidos entre sí por enlaces peptídicos. Tras la síntesis, una proteína se pliega en una conformación tridimensional, fundamental para su función biológica. Las interacciones entre los aminoácidos que lo constituyen guían el plegamiento de las proteínas y, por tanto, la estructura de las proteínas depende principalmente de su secuencia de aminoácidos.

La estructura de las proteínas es fundamental para su función biológica

Las proteínas realizan una amplia gama de funciones biológicas, como catalizar reacciones químicas, proporcionar defensa inmunológica, almacenamiento, transporte, comunicación celular, movimiento y soporte estructural. La función de una proteína depende principalmente de reconocer y unir otras moléculas, de forma análoga a una cerradura y una llave. Por tanto, la actividad específica de cada proteína depende de su arquitectura tridimensional única.

Para que una proteína sea funcional, debe plegarse con precisión. La mayoría de las proteínas pasan por varias formas intermedias antes de plegarse en la estructura biológicamente activa más estable. El mal plegamiento de las proteínas puede afectar el funcionamiento general de la célula. La acumulación de proteínas mal plegadas o desplegadas en humanos provoca fibrosis quística, Alzheimer, Parkinson, esclerosis lateral amiotrófica y enfermedad de Creutzfeldt-Jakob.

Determinantes críticos de la estructura de las proteínas

Las proteínas están formadas por una o más cadenas de aminoácidos llamadas polipéptidos. Un polipéptido se sintetiza como una cadena lineal que rápidamente se pliega sobre sí misma para formar una estructura tridimensional. Los términos polipéptido y proteína a veces se usan indistintamente, pero lo más común es que un polipéptido plegado que puede realizar una función biológica se llame proteína. La estructura de una proteína generalmente se describe en cuatro niveles: primario, secundario, terciario y cuaternario. La mayoría de los polipéptidos se pliegan en una estructura terciaria globular compacta general, como la hemoglobina, la proteína transportadora de oxígeno en la sangre. Algunas proteínas, como las queratinas, forman fibras largas y se encuentran comúnmente en el cabello y las uñas. Las proteínas globulares son solubles en agua, a diferencia de las proteínas fibrosas.

La secuencia de aminoácidos en la cadena polipeptídica es el principal determinante de su estructura. La secuencia de aminoácidos determina el tipo y ubicación de las estructuras secundarias. Además, la estructura terciaria general de una proteína se estabiliza predominantemente mediante enlaces químicos entre las cadenas laterales de aminoácidos, los grupos químicos únicos que distinguen los aminoácidos entre sí. Estas cadenas laterales están cargadas (positiva o negativamente), polares sin carga o no polares.

Los aminoácidos tienen características físicas y químicas únicas dependiendo de sus grupos de cadenas laterales. Por ejemplo, los aminoácidos polares y cargados interactúan con el agua para formar enlaces de hidrógeno y se denominan hidrófilos. Por el contrario, los aminoácidos apolares evitan las interacciones con el agua y se denominan hidrofóbicos. Por lo tanto, cuando una proteína se pliega en un entorno celular, las cadenas laterales de aminoácidos hidrófobos quedan enterradas en el núcleo de la proteína, lejos del entorno acuoso. Por el contrario, las cadenas laterales de aminoácidos hidrófilos están expuestas en la superficie de la proteína.

Los aminoácidos hidrófobos estrechamente empaquetados en el núcleo de la proteína conducen a la formación de interacciones débiles de Van der Waals entre los grupos de las cadenas laterales. Estas fuerzas de Van der Waals imparten estabilidad adicional a la proteína plegada. Los aminoácidos polares expuestos en la superficie de la proteína son libres de formar enlaces de hidrógeno con moléculas de agua u otras cadenas laterales de aminoácidos polares. Los aminoácidos con carga positiva y negativa también están presentes en el exterior de una proteína, donde forman enlaces iónicos con otros aminoácidos cercanos con carga opuesta.

Se forman enlaces disulfuro entre dos grupos sulfhidrilos, o SH, en el aminoácido cisteína. Se trata de una interacción robusta que actúa como refuerzo de la proteína plegada. Los enlaces disulfuro bloquean la proteína plegada en su conformación tridimensional más favorecida. El plegamiento adecuado de una proteína también depende de otros factores del entorno celular como el pH, la concentración de sal, la temperatura, etc. La alteración de las condiciones físicas y químicas en un entorno proteico afecta las interacciones químicas que mantienen unida a la proteína y puede provocar que la proteína se pliegue mal. o desplegarse y perder su función biológica, un proceso conocido como desnaturalización de proteínas.

Plegado de proteínas

Las proteínas son cadenas de aminoácidos unidos entre sí por enlaces peptídicos. Tras la síntesis, una proteína se pliega en una conformación tridimensional, fundamental para ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Protein Structure

Estructura de las proteínas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

how amino acid sequence shapes proteins

Proteins get their shape from the order of amino acids in a polypeptide chain. After a protein is made, the chain folds into a three-dimensional form that is needed for it to work. The way amino acids interact with one another guides this folding.

Protein structure matters because proteins do many jobs in cells. They can speed up chemical reactions, help with immune defense, store materials, carry substances, send cell signals, support movement, and provide structure. A protein usually works by binding to another molecule, much like a lock and key. That is why its specific three-dimensional shape is so important.

To be functional, a protein must fold correctly. Many proteins pass through several intermediate forms before reaching the most stable and biologically active shape. When proteins misfold, they can disrupt cell function. In humans, misfolded or unfolded proteins are linked with cystic fibrosis, Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and Creutzfeldt-Jakob disease.

Proteins are made of one or more amino acid chains called polypeptides. A polypeptide starts as a linear chain and then folds quickly into a three-dimensional structure. The words polypeptide and protein are sometimes used interchangeably, but a folded polypeptide that can do a job is usually called a protein. Protein structure is often described at four levels: primary, secondary, tertiary, and quaternary.

Most polypeptides fold into a compact, globular tertiary structure. Hemoglobin, the oxygen-carrying protein in blood, is an example. Some proteins, such as keratins, form long fibers and are found in hair and nails. Globular proteins are usually soluble in water, while fibrous proteins are not.

The amino acid sequence is the main factor that determines protein shape. It helps decide where secondary structures form and how the full tertiary structure develops. Side chains, the chemical groups that make amino acids different from one another, stabilize the folded protein. These side chains may be charged, polar but uncharged, or non-polar.

Polar and charged amino acids interact with water and are called hydrophilic. Non-polar amino acids avoid water and are called hydrophobic. When a protein folds in a cell, hydrophobic side chains are usually buried in the core, away from water, while hydrophilic side chains stay on the surface. Tight packing in the hydrophobic core creates weak Van der Waals interactions that help stabilize the structure.

Hydrophilic side chains on the outside can form hydrogen bonds with water or with other polar side chains. Positively and negatively charged amino acids can also form ionic bonds with nearby oppositely charged amino acids. Another strong bond, called a disulfide bond, forms between two sulfhydryl, or SH, groups on cysteine. This bond helps lock the protein into its most stable three-dimensional shape.

Protein folding also depends on the cell’s environment. pH, salt concentration, and temperature can affect the chemical interactions that hold a protein together. If these conditions change, a protein may misfold or unfold and lose its function. This process is called protein denaturation.

How Amino Acid Sequence Shapes Proteins

what are proteins?

Protein Building Blocks and Folding

Proteins are built from amino acids linked by peptide bonds. Long chains of amino acids are often called polypeptides, and the terms proteins and polypeptides are sometimes used the same way. In this context, polypeptides with a molecular weight below 10,000 daltons are called polypeptides, while proteins have a higher molecular weight. Very short chains with fewer than 20 amino acids are called peptides or oligopeptides. Amino acids are the basic units of proteins. Each amino acid has a...

protein organization

Protein Folding Levels and Bonds

Proteins are built from amino acids and folded into shapes that support many cell jobs. They help with DNA replication, molecular transport, catalysis, and structural support. Their function depends on how their amino acids are arranged and folded. Protein structure is organized in levels. The primary structure is the amino acid sequence in a polypeptide chain. Amino acids are joined by peptide bonds, and the chain has two ends: the amino terminus, or N-terminus, and the carboxyl terminus, or...

protein folding

Proteins get their shape from the order of amino acids in a polypeptide chain. After a protein is made, the chain folds into a three-dimensional form that is needed for it to work. The way amino acids interact with one another guides this folding. Protein structure matters because proteins do many jobs in cells. They can speed up chemical reactions, help with immune defense, store materials, carry substances, send cell signals, support movement, and provide structure. A protein usually works...

protein families

Protein Families and Superfamilies

Protein families and superfamilies group proteins with shared features. These groups help scientists organize proteins by common structure, function, or evolutionary history. The classification can show how related proteins are connected across different organisms. A protein family usually includes proteins that are closely related. A superfamily is a broader group that can include several families with more distant relationships. These categories help explain why some proteins share similar...

conservation of protein domains

Protein Domains Shared Across Proteins

Protein domains are shared structural and functional parts of proteins. A domain is a region that can often be found in more than one protein, even when the full proteins are different. This conservation means that a protein domain may keep a similar shape or role across related proteins. Because of that, scientists can compare proteins by looking for domains that stay the same. Conserved domains help reveal how proteins are related and how they may work. The topic of protein domain...

globular and fibrous proteins

Protein Shapes: Globular vs Fibrous

Proteins can have globular or fibrous shapes, and these shapes help explain how they work in the body. Globular proteins are compact and usually fold into rounded forms. Fibrous proteins are long, extended molecules that often provide support and structure. The shape of a protein is tied to its function. Globular proteins often take part in chemical jobs in cells, while fibrous proteins are better suited for strength and stability. These structural differences make the two groups easy to...

intrinsically disordered proteins

Flexible Protein Regions and Disorder

Intrinsically disordered proteins have flexible regions that do not settle into one fixed shape. Instead, these proteins can remain dynamic and change form as they move through the cell. This flexibility is an important part of their structure and function. Many proteins need a stable folded shape to work properly. Intrinsically disordered proteins are different because they may lack a single rigid structure under normal conditions. Their shifting shape can help them take part in cell...

protein complex assembly

Protein Complex Formation and Function

Protein complex formation explains how proteins join together to carry out specific jobs in cells. These groups are called protein complexes, and they can form in more than one way. Some complexes are homomeric, which means they contain the same kind of protein subunit. Others are heteromeric, which means they contain different protein subunits. The assembly process helps show how protein shape and subunit choice affect function. When proteins combine, the resulting complex can behave...

conjugated proteins

Conjugated Proteins and Their Bound Groups

Conjugated proteins are proteins that include a nonprotein part called a prosthetic group. This added group helps give the protein its full structure or function. The video explains how the protein part and the bound group work together. Several common types of conjugated proteins are named by the kind of group attached. Nucleoproteins contain nucleic acids. Glycoproteins contain carbohydrate groups, and lipoproteins contain lipid groups. Other examples include phosphoproteins, which have...

amyloid fibrils

Amyloid Fibrils and Protein Aggregation

Amyloid fibrils are protein aggregates with a very specific structure. They are made when proteins misfold and stick together in long, ordered fibers. This structure makes them different from many other protein clumps. Amyloid fibrils are important in biology because they are linked to protein aggregation. Protein aggregation means proteins build up into groups instead of staying properly folded and separate. In many cases, this process is associated with disease and abnormal cell function. <br...

key terms and concepts

Learn how amino acid sequence, side-chain interactions, and cell conditions shape protein structure, stability, and function in high school biology.

How Amino Acid Sequence Shapes Proteins | JoVE K12

cell biology

JoVE Core Biología Celular ilustra procesos celulares complejos mediante completos vídeos animados fáciles de entender. Esta colección se centra en los componentes esenciales de las células y su funcionamiento, incluyendo los orgánulos y las membranas, el transporte celular y el metabolismo energético celular. Todo este material se complementa con los vídeos de científicos en acción, que muestran la aplicación de la biología celular en experimentos reales de investigación.

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-1.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Cell Structure

Background
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Cytoplasm

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The Nucleus

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The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

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Chromosome Structure

Base-pairing and DNA Repair

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RNA Structure

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Protein Families

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Conservation of Protein Domains

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Globular and Fibrous Proteins

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Intrinsically Disordered Proteins

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Protein Complex Assembly

Protein and Protein Structures

Conjugated Proteins

Proteins: From Genes to Degradation

Amyloid Fibrils

What are Proteins?

Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino ...

Ligand Binding Sites

Protein Organization

Proteins are polymers of amino acid residues. They are versatile and responsible for different cellular functions, including DNA replication, molecular ...

Protein-Protein Interfaces

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to ...

Conserved Binding Sites

Cofactors and Coenzymes

Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic ...

Cooperative Allosteric Transitions

Protein Kinases and Phosphatases

GTPases and their Regulation

Covalently Linked Protein Regulators

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

Levels of Organization

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth&#x27;s biosphere. ...

Animal and Plant Cell Structure

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structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

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Overview of Human Digestion

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. ...

Anatomy of the Intestines

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, ...

Accessory Organs

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it like the mouth, stomach, or intestine do. ...

Lipid Digestion

Lipids are large molecules that are generally not water-soluble. Since most of the digestive enzymes in the human body are water-based, there are specific ...

Protein Digestion

Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of ...

Carbohydrate Digestion

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. ...

What is a Nervous System?

Overview

The nervous system is the collection of specialized cells responsible for maintaining an organism&rsquo;s internal environment and coordinating ...

The Parasympathetic Nervous System

Overview

The parasympathetic nervous system is one of the two major divisions of the autonomic nervous system. This parasympathetic system is responsible ...

The Sympathetic Nervous System

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Oogenesis

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Fertilization

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What is the Skeletal System?

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an-introduction-to-the-zebrafish-danio-rerio

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Physiology of the Circulatory System

Homeostasis
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Anatomy of the Circulatory System

The human circulatory system consists of blood, blood vessels that carry blood away from the heart, around the body, and back to the heart, and the heart ...

Measuring Blood Pressure
ExpandTo prepare for the blood pressure exercise, simply place the appropriate number of alcohol swabs, sphygmomanometers, and ...

Anatomy of the Heart

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Measuring Circulatory System Function in Humans
ExpandBefore starting the experiment go to the front of the room and collect an alcohol swab, a ...

Blood Flow

Blood is pumped by the heart into the aorta, the largest artery in the body, and then into increasingly smaller arteries, arterioles, and capillaries. The ...

What Are Osmoregulation and Excretion?

Organisms must keep bodily fluids at a constant temperature and pH while maintaining specific solute concentrations in order to support life functions. ...

Blood Withdrawal I

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Kidney Structure

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Blood Withdrawal II

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN
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What is the Immune System?

Overview

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Bone Remodeling

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Spermatogenesis

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Bone Structure

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

What is Homeostasis?

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Negative and Positive Feedback

Homeostatic Imbalance

Homeostasis is the maintenance of a stable internal environment within the body, which is crucial for the proper functioning of cells, tissues, organs, ...

pH Homeostasis

Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

HS-LS1-3

How Amino Acid Sequence Shapes Proteins

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