Name: protein regulation by covalent bonds
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 2 min 4 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

Covalently Linked Protein Regulators

חלבונים רבים מווסתים על ידי מולקולות הקשורות באופן קוולנטי, כולל קבוצות פונקציונליות, כגון מתיל או אצטיל moieties, וחלבונים קטנים, כגון ubiquitin.
קשרים קוולנטיים מתרחשים על חומצות אמינו ספציפיות בשרשרת הפוליפפטידים. לדוגמה, קבוצות פוספטים קשורות באופן קוולנטי לסרין, תראונין או טירוזין; קבוצות מתיל ואצטיל קשורות לליזין; ויוביקוויטין קשור לשאריות ליזין, ציסטאין, סרין או תראונין.
אנזים או זוג אנזימים מזרזים באופן הפיך את השינויים שלאחר התרגום. אצטילטרנספראז יכול ליצור אצטילט של חלבון, ואילו דאצטילאז יכול להסיר את הקבוצה מאוחר יותר.
שינויים אלה יכולים לשנות את תפקוד החלבון או את מיקומו בתא.
לדוגמה, אצטילציה של חלבוני היסטון מווסתת את ביטוי הגנים על ידי פתיחת מבנה הדנ"א כדי להפעיל שעתוק גנים. מתילציה של חלבוני היסטון, לעומת זאת, ידועה כמדכאת שעתוק על ידי הידוק המבנה. 
דוגמה נוספת היא p53, חלבון מדכא גידולים רב-תחומי שעובר מספר שינויים קוולנטיים בתגובה ללחץ. חשיפה לחומרים מזיקים לדנ"א, כגון קרינת UV וגמא, עלולה לגרום לזרחון של החלבון. 
הזרחן משפר את היציבות ומפעיל p53, גורם לו להיקשר לדנ"א שניזוק מהקרינה ומונע מתאים עם דנ"א שעבר מוטציה להתחלק ללא שליטה.
בנוסף לזרחון, סוגים שונים של שינויים המתרחשים במולקולת חלבון יחידה, כגון p53, מאפשרים לה לשלוט במדויק בתפקודיה כגון מעצר מחזור התא, תיקון DNA ואפופטוזיס של תא.

<ol>
	<li>1מזהה PDB: 1UBQ 
	Vijay-Kumar, S., Bugg, C.E., Cook, W.J.(1987) מבנה של יוביקוויטין מעודן ברזולוציה של 1.8 אמפר. J מול ביול 194: 531-544. DOI: 10.1016/0022-2836(87)90679-6</li>
	<li>H.M. ברמן, ג 'יי ווסטברוק, Z. Feng, ג 'גילילנד, T.N. Bhat, H. Weissig, I.N. Shindyalov, P.E. בורן. (2000) בנק נתוני החלבונים מחקר חומצות גרעין, 28: 235-242.</li>
	<li>D. Sehnal, A.S. Rose, J. Kovca, S.K. Burley, S. Velankar (2018) Mol*: לקראת ספרייה משותפת וכלים לגרפיקה מולקולרית באינטרנט MolVA/EuroVis Proceedings. doi:10.2312/molva.20181103</li>
	<li>אלברטס ואחרים, מהדורה שישית; עמודים 157-158, 165-166</li>
	<li>לה, ד 'ד', ופוג'ימורי, ד' ג' (2012). חלבון וחומצות גרעין מתילציה אנזימים: מנגנונים וויסות. דעה נוכחית בביולוגיה כימית, 16(5-6), 507-515. doi:10.1016/j.cbpa.2012.09.014</li>
	<li>Khidekel, N., & Hsieh-Wilson, L. C. (2004). "מרכזייה מולקולרית" – שינויים קוולנטיים בחלבונים והשפעתם על השעתוק. כימיה אורגנית וביומולקולרית, 2(1), 1-7.</li>
	<li>מקליין, נ 'ג'יי והופ, ט. ר. (2009). ויסות p53 על ידי זרחון: מודל לאופן שבו אותות שונים משתלבים במסלול p53. הזדקנות, 1(5), 490.</li>
</ol>

מווסתי חלבונים מקושרים קוולנטית

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חלבונים יכולים לעבור סוגים רבים של שינויים לאחר תרגום, לעתים קרובות בתגובה לשינויים בסביבתם. שינויים אלה ממלאים תפקיד חשוב בתפקוד וביציבות של חלבונים אלה. מולקולות מקושרות קוולנטיות כוללות קבוצות פונקציונליות, כגון קבוצות מתיל, אצטיל ופוספט, וגם חלבונים קטנים, כגון יוביקוויטין. ישנם כ-200 סוגים שונים של מווסתים קוולנטיים שזוהו.

קבוצות אלו משנות חומצות אמינו ספציפיות בחלבון. קבוצות פוספט יכולות להיות מחוברות רק בקוולנטיות לחומצות האמינו סרין, ת'רונין וטירוזין, בעוד שקבוצות מתיל ואצטיל יכולות להיות קשורות רק לליזין. קבוצות אלו מוספות לחלבון ומוסרות ממנו על ידי אנזים או זוג אנזימים. לדוגמה, אצטילטרנספראז מוסיף קבוצת אצטיל לחלבון, ודאצטילאז יכול להסיר אותה. לכל אחת מהמודיפיקציות הללו יכולות להיות השפעות שונות על החלבון שאליו הוא מחובר בהתאם למספר ולמיקום של השינויים. כאשר מולקולת יוביקוויטין אחת מקושרת באופן קוולנטי לקולטן מסוים משטח התא, חלבון זה מכוון לאנדוציטוזיס; מצד שני, כאשר מספר אוביקוויטין מקושרים ביחד מחוברים לחלבון זה, הוא יסומן כמטרה לפירוק פרוטאוליטי.

חלבון בודד יכול לעבור שינויים מרובים בו זמנית כדי לשלוט בתפקודו. דוגמה ידועה אחת לחלבון המווסת על ידי שינויים קוולנטיים מרובים היא החלבון מדכא הגידול, p53. p53 עובר מגוון של שינויים בתגובה לסוגים שונים של מתח, כולל קרינה וחומרים מסרטנים. שינויים מסוימים כוללים זרחון, אצטילציה וסומוילציה בתגובה לקרינת UV וגמא. האתרים וסוגי השינויים יכולים להשתנות בהתאם לגורם הלחץ. מחקרים הראו כי קרינת UV וקרינת גמא יכולה לגרום לזרחון של סרין 33, אך סרין 392 יכול להיות זרחן כאשר הוא נחשף ל-UV אך לא לקרינת גמא. סוגים אחרים של מתח, כגון חשיפה להיפוקסיה, אנטי-מטבוליטים ואקטינומיצין D, יכולים לגרום לאצטילציה של p53. השינויים יכולים גם להשתנות בין סוגי תאים ואורגניזמים שונים.

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חלבונים יכולים לעבור סוגים רבים של שינויים לאחר התרגום, לעתים קרובות בתגובה לשינויים בסביבתם. שינויים אלה משחקים ...

Education

JoVE Core

Cell Biology

ביולוגיה של התא

Unit 1

יחידה 1

Protein Function

תפקוד חלבונים

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

protein regulation by covalent bonds

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves.

Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function.

Covalently linked protein regulators are an important part of cell control and signaling. They help cells turn protein functions on or off at the right time. This type of regulation is a key idea in molecular biology and protein function.

Protein Regulation by Covalent Bonds

ligand binding sites

Ligand Binding Sites in Proteins

Ligand binding sites are specific parts of a protein where a ligand can attach. A ligand is a molecule that binds to another molecule, often to help start or change a biological process. These sites matter because the shape and chemistry of the protein help determine which ligands can fit and bind. Proteins do not bind every ligand in the same way. The binding site provides a matching surface that supports a close interaction. In many cases, this interaction is important for how cells respond...

protein-protein interfaces

Protein Binding Surfaces and Contacts

Protein binding surfaces and contacts help proteins recognize and attach to each other. These interfaces are the regions where two proteins meet and interact. They are important for many cell processes and for how proteins work together. A protein-protein interface is not just a random touch point. It is shaped by the three-dimensional form of each protein. The matching surfaces allow a stable interaction to form when the proteins fit together well. Studying these interfaces helps explain how...

conserved binding sites

Conserved Binding Sites in Protein Families

Conserved binding sites are regions on proteins that stay similar across related proteins. These shared areas often help proteins interact with the same molecules. For this reason, they are useful clues when comparing protein families. A conserved site can help identify where a protein binds. It can also show which parts of the protein are important for function. When the same pattern appears in several proteins, it suggests that the site has been kept through evolution. Scientists look at...

cofactors and coenzymes

Enzyme Helpers: Metals and Vitamins

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors. Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These...

cooperative allosteric transitions

Allosteric Changes in Protein Shape

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule. The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens...

protein kinases and phosphatases

Protein Kinases and Phosphatases in Cell Control

Protein kinases and phosphatases help control how proteins work in cells. Kinases add phosphate groups to proteins. Phosphatases remove those phosphate groups. This phosphorylation and dephosphorylation process can change a protein’s shape and activity. It is one way cells turn protein function on or off at the right time. These changes also help cells respond to signals and manage many cell activities. Together, protein kinases and phosphatases keep cellular signaling balanced. When one adds...

gtpases and their regulation

GTPase Molecular Switches and Control

GTPases are molecular switches that help control cell activity. They bind guanosine triphosphate, or GTP, and can change between active and inactive states. This switch-like behavior makes them important in many cell processes. The protein is active when GTP is bound and inactive when guanosine diphosphate, or GDP, is bound. GTPases can also turn themselves off by breaking down GTP into GDP. This built-in control helps cells regulate when the protein is on or off. Their activity is regulated...

covalently linked protein regulators

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves. Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function. Covalently linked...

protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

Modular Protein Complexes in Cells

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior. A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change. The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins...

mechanical protein function

Proteins That Generate Cell Movement

Mechanical proteins help cells and tissues move. They turn chemical energy into force and motion. This process is important in many biological systems. These proteins are also called motor proteins. They interact with cell structures and can produce directed movement. In muscle cells, they support contraction. In other cells, they help with transport and shape changes. Mechanical protein function is a key part of how living systems work. It links protein activity to movement at the cellular...

structural protein function

Structural Proteins in Cells and Tissues

Structural proteins help cells and tissues keep their shape and strength. They are an important part of living systems because they provide support where it is needed most. Many structural proteins form fibers or other sturdy forms that resist stretching and wear. These proteins work as building materials in the body and help keep structures stable over time. Examples of structural proteins include collagen, actin, myosin, and keratin. Each one supports a different part of the body, but all...

protein networks

Mapping Protein Interaction Networks

Protein interaction networks show how proteins work together inside a cell. These networks help scientists see which proteins connect with each other and how those links support cell activity. Researchers often use online tools to build and study these networks. The transcript points to IntAct and STRING as examples of resources that can help predict and organize protein interactions. These tools make it easier to compare protein links and look for patterns in the network. Protein networks...

key terms and concepts

Learn how covalent bonds can regulate proteins by changing activity, location, and stability. A clear K12 summary of protein control in cells.

Protein Regulation by Covalent Bonds | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Characteristics of Life

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Conservation of Protein Domains

Transcription

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Globular and Fibrous Proteins

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

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Protein Complex Assembly

Protein and Protein Structures

Conjugated Proteins

Proteins: From Genes to Degradation

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Ligand Binding Sites

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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

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

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Overview of Human Digestion

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Anatomy of the Intestines

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The Parasympathetic Nervous System

Overview

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The Sympathetic Nervous System

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Homeostasis
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Measuring Circulatory System Function in Humans
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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

What is Homeostasis?

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Negative and Positive Feedback

Homeostatic Imbalance

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pH Homeostasis

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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

Protein Regulation by Covalent Bonds

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