Name: how protein shape determines function
Uploaded: 2023-04-30T18:28:47.000Z
Duration: 2 min 15 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 and Protein Structures

Las proteínas son polímeros de aminoácidos unidos mediante enlaces peptídicos. La mayoría de las proteínas se pliegan en estructuras tridimensionales específicas para realizar su función. La estructura de las proteínas se clasifica en cuatro categorías:primaria, secundaria, terciaria y cuaternaria.La secuencia lineal de aminoácidos en la proteína es su estructura primaria. Estas secuencias se leen en el orden de síntesis del polímero, desde el extremo N-terminal, el extremo amino libre, hasta el C-terminal, el extremo carboxilo libre. Las estructuras secundarias se forman a través de enlaces de hidrógeno entre el oxígeno del grupo carbonilo de un aminoácido y el hidrógeno del grupo amino de otro.Las estructuras secundarias comunes incluyen hélices alfa y láminas plegadas beta Estas y otras estructuras de conexión, como los giros β, interactúan más para formar la estructura tridimensional de la proteína, conocida como estructura terciaria. La formación de la estructura terciaria se produce debido a interacciones entre los grupos R de los aminoácidos. Los grupos R con cargas opuestas pueden formar enlaces iónicos y el azufre en dos cisteínas puede formar un puente disulfuro covalente.Otros contribuyentes incluyen a las interacciones hidrofóbicas entre cadenas laterales hidrofóbicas y enlaces de hidrógeno entre cadenas laterales polares. Además, algunas proteínas forman estructuras cuaternarias, conjuntos de dos o más cadenas polipeptídicas. Por ejemplo, la hemoglobina es una proteína formada por cuatro subunidades, dos α y dos β.Los científicos pueden usar la estructura de una proteína para predecir su función y ubicación en una célula. Las proteínas en el citoplasma celular tienen aminoácidos hidrófilos en sus superficies que interactúan con el agua en el citoplasma y tienen núcleos hidrófobos. Por el contrario, las proteínas presentes en las membranas celulares a menudo tienen aminoácidos hidrófobos en la superficie que interactúan con los glicerofosfolípidos en la membrana y tienen núcleos hidrófilos.

<ol>
	<li>Nelson, D. L., & Cox, M. M. (2008). Principios de bioquímica de Lehninger (5ª ed.). W.H. Freeman. Págs. 113-140</li>
	<li>Estructura cristalina de la hemoglobina en estado T con oxígeno unido a las cuatro hemas.Paoli, M., Liddington, R., Tame, J., Wilkinson, A., Dodson, G. (1996) J Mol Biol 256: 775</li>
</ol>

proteínas y estructuras proteicas

Las proteínas son una de las moléculas orgánicas más abundantes en los sistemas vivos y tienen la gama más diversa de funciones entre todas las macromoléculas. Las proteínas pueden ser estructurales, reguladoras, contráctiles o protectoras. Pueden servir en el transporte, almacenamiento o en las membranas; o pueden ser toxinas o enzimas. Sus estructuras, al igual que sus funciones, varían mucho. Sin embargo, todos son polímeros de aminoácidos dispuestos en una secuencia lineal.
 La forma de una proteína es crítica para su función. Por ejemplo, una enzima puede unir un sustrato específico en su sitio activo. Si este sitio activo se altera debido a cambios locales o cambios en la estructura general de la proteína, la enzima puede ser incapaz de unirse al sustrato. Para entender cómo la proteína obtiene su forma final o conformación, necesitamos entender los cuatro niveles estructurales de las proteínas: Primaria, secundaria, terciaria y cuaternaria.
 Estructura primaria
 La secuencia única de aminoácidos en una cadena polipeptídica es su estructura primaria. Por ejemplo, la hormona pancreática insulina tiene dos cadenas de polipéptidos, A y B, y están unidas por enlaces de disulfuro. El aminoácido N-terminal de la cadena A es glicina, mientras que el aminoácido C-terminal es asparagina.  Las secuencias de aminoácidos en las cadenas A y B son únicas de la insulina.
 El gen que codifica la proteína determina en última instancia la secuencia única para cada proteína. Un cambio en la secuencia de nucleótidos de la región codificadora del gen puede llevar a añadir un aminoácido diferente a la cadena polipeptídica en crecimiento, causando un cambio en la estructura y función de las proteínas. En la anemia de células falciformes, la cadena de hemoglobina β tiene una sola sustitución de aminoácido, causando un cambio en la estructura y función de la proteína. Específicamente, la valina en la cadena β sustituye al aminoácido ácido glutámico. Debido a este cambio de un aminoácido en la cadena, las moléculas de hemoglobina forman fibras largas que distorsionan los glóbulos rojos bicóncavos, o en forma de disco, y los hace asumir una forma de media luna o “hoz”, que obstruye los vasos sanguíneos. Esto puede conducir a una miríada de problemas de salud serios tales como disnea, vértigos, dolores de cabeza, y dolor abdominal para aquellos afectados por esta enfermedad.
 Estructura secundaria
 El plegamiento local del polipéptido en algunas regiones da lugar a la estructura secundaria de la proteína. Las más comunes son las estructuras de hoja β y de hélice α. Ambas estructuras se mantienen por puentes de hidrógeno. Los puentes de hidrógeno se forman entre el átomo de oxígeno en el grupo carbonilo en un aminoácido y otro aminoácido que está cuatro aminoácidos más adelante a lo largo de la cadena.
 Cada giro helicoidal en una hélice alfa tiene 3,6 residuos de aminoácidos. Los grupos R del polipéptido (los grupos variantes) sobresalen de la cadena α. En la hoja β plegada, los puentes de hidrógeno entre los átomos de la columna vertebral de la cadena polipeptídica forma los pliegues β. Los grupos R están unidos a los carbonos y se extienden por encima y por debajo de los pliegues. Los segmentos plegados se alinean de forma paralela o antiparalela entre sí, y se forman puentes de hidrógeno entre el átomo de hidrógeno parcialmente positivo en el grupo amino y el átomo de oxígeno parcialmente negativo en el grupo carbonilo de la columna vertebral del péptido. Las estructuras de hélice α y hoja β plegada están en la mayoría de las proteínas globulares y fibrosas, y juegan un papel estructural importante.
 Estructura terciaria
 La estructura tridimensional única del polipéptido es su estructura terciaria. Esta estructura se debe en parte a las interacciones químicas en la cadena de polipéptidos. Principalmente, las interacciones entre los grupos R crean la compleja estructura terciaria tridimensional de la proteína. La naturaleza de los grupos R en los aminoácidos implicados puede contrarrestar la formación de los puentes de hidrógeno que describimos para las estructuras secundarias estándar. Por ejemplo, los grupos R con cargas similares se repelen unos a otros, y aquellos con cargas diferentes se atraen mutuamente (enlaces iónicos). Cuando se produce el plegamiento de las proteínas, los grupos hidrofóbicos R de los aminoácidos no polares se encuentran en el interior de la proteína; mientras que los grupos hidrofílicos R se encuentran en el exterior. Las interacciones entre las cadenas laterales de la cisteína forman enlaces disulfuro en presencia de oxígeno, el único enlace covalente que se forma durante el plegamiento proteico.
 Todas estas interacciones, débiles y fuertes, determinan la forma tridimensional final de la proteína. Cuando una proteína pierde su forma tridimensional, puede que ya no sea funcional.
 Estructura cuaternaria
 En la naturaleza, algunas proteínas se forman a partir de varios polipéptidos, o subunidades, y la interacción de estas subunidades forma la estructura cuaternaria. Las interacciones débiles entre las subunidades ayudan a estabilizar la estructura general. Por ejemplo, la insulina (una proteína globular) tiene una combinación de puentes de hidrógeno y enlaces disulfuro que hacen que se aglutine en su mayoría en forma de bola. La insulina comienza como un solo polipéptido y pierde algunas secuencias internas en presencia de modificación post-traduccional después de formar los enlaces disulfuro que mantienen juntas las cadenas restantes. La seda (una proteína fibrosa), sin embargo, tiene una estructura de hoja β plegada que es el resultado de puentes de hidrógeno entre cadenas diferentes.
 Este texto ha sido adaptado de<a href="https://openstax.org/books/biology-2e/pages/3-4-proteins"> Openstax, Biología 2e, Capítulo 3.4: Proteínas</a>.

Proteínas y Estructuras Proteicas

Las proteínas son una de las moléculas orgánicas más abundantes en los sistemas vivos y tienen la gama más diversa de funciones de todas las macromoléculas. Las proteínas pueden ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Biochemistry of the Cell

Bioquímica de la célula

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

how protein shape determines function

Proteins are essential molecules in living things, and their shape affects how they work. Protein structure is described at several levels, including primary, secondary, tertiary, and quaternary structure. These levels help explain how a protein is built and how its final form supports its job.

Primary structure is the sequence of amino acids in a protein. Secondary structure forms when parts of the chain fold into regular patterns. Tertiary structure is the overall three-dimensional shape of one protein chain. Quaternary structure appears when more than one protein chain joins together to make a working protein.

The video also shows how protein structure can be represented in different ways. A simple line drawing can show the amino acid sequence. Other models can show folding and the full 3D shape. These visual forms help students compare levels of structure and see why protein shape matters.

How Protein Shape Determines Function

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

Elements in the Human Body and Periodic Table

Elements are the smallest units of matter that cannot be broken down further by chemical processes. Scientists know 118 elements, but not all of them occur naturally. Only a small number are essential for life, and living matter depends mostly on carbon, nitrogen, hydrogen, and oxygen. The periodic table organizes elements by their physical and chemical properties. Each square shows the element name, chemical symbol, atomic number, and atomic weight. The atomic number is the number of protons...

functional groups

Functional Groups in Organic Molecules

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types of chemical bonds

Chemical Bonds and How Atoms Join

Chemical bonds hold atoms together and help explain how different substances form. In chemistry, the main bond types are ionic bonds, covalent bonds, and metallic bonds. Ionic bonds form when electrons move from one atom to another. Covalent bonds form when atoms share electrons. Metallic bonds occur in metals, where electrons are held in a shared arrangement that gives metals their characteristic behavior. Understanding these bond types helps students compare how atoms connect in different...

noncovalent attractions in biomolecules

Biomolecule Interactions Without Covalent Bonds

Biomolecules often stay together through noncovalent attractions instead of covalent bonds. These weaker interactions help molecules recognize each other and form structures needed for life. The main noncovalent attractions are hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. Each one works in a different way, but all of them can influence how biomolecules fold, bind, and behave in cells. Hydrogen bonds form when a hydrogen atom is attracted to...

polymers

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what are lipids?

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structure of lipids

How Lipid Molecules Are Built

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chemistry of carbohydrates

Carbohydrate Structure and Bonding

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nucleic acids

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protein and protein structures

Proteins are essential molecules in living things, and their shape affects how they work. Protein structure is described at several levels, including primary, secondary, tertiary, and quaternary structure. These levels help explain how a protein is built and how its final form supports its job. Primary structure is the sequence of amino acids in a protein. Secondary structure forms when parts of the chain fold into regular patterns. Tertiary structure is the overall three-dimensional shape of...

ph regulation in cells

Cell pH and Organelle Balance

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chemistry of the cell

Cell Chemistry: Water, Ions, and Molecules

Cell chemistry explains the substances that make cells work. Water is the main component of cells, and it supports the chemical reactions that keep life going. Cells also contain organic molecules, which are carbon-based compounds, and inorganic ions, which are charged particles needed for cell function. Organic molecules in cells include carbohydrates, lipids, proteins, and nucleic acids. These molecules have different roles, but together they build cell structures, store energy, and carry...

key terms and concepts

Learn how proteins are built and folded through primary, secondary, tertiary, and quaternary structure, and how protein shape affects function.

How Protein Shape Determines Function | 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.

Florida Department of Education

SC.912.L.18

SC.912.L.18.1

SC.912.L.18.4

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-1.

Georgia Standards of Excellence

9-12

Biology

SB6.c

Characteristics of Life

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

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Cell Structure

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Cytoplasm

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The Nucleus

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Globular and Fibrous Proteins

Translation

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Intrinsically Disordered Proteins

Ribosomes

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Protein Complex Assembly

Conjugated Proteins

Proteins: From Genes to Degradation

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Protein-Protein Interfaces

Protein Folding

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Conserved Binding Sites

Cofactors and Coenzymes

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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.]

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Protein Digestion

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Carbohydrate Digestion

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What is a Nervous System?

Overview

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The Parasympathetic Nervous System

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The Sympathetic Nervous System

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Fertilization

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Physiology of the Circulatory System

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Blood Flow

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What Are Osmoregulation and Excretion?

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Blood Withdrawal I

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Blood Withdrawal II

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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

How Protein Shape Determines Function

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