Difference Between Co and Post Translational Modification

The key difference between co and post translational modification is that co-translational modification is a type of protein modification which occurs during the synthesis while post-translational modification is a type of modification that occurs after the initial synthesis is completed.

Protein is an essential macronutrient for living organisms. Genes encode proteins via gene expression. Gene expression takes place through two major steps: transcription and translation. Gene expression is a complex process which is tightly regulated in order to produce an accurate and fully functional protein. Hence, there are modifications occurring during the gene expression. There are three levels of protein modifications. They are pre translational, co-translational and post-translational modifications. Co-translational modifications take place during the translation process while post-translational modifications take place after translation or protein synthesis. As a result of all these modifications, a mature protein product which is crucial for cells is formed at the end of the gene expression.

CONTENTS

1. Overview and Key Difference
2. What is Co Translational Modification
3. What is Post Translational Modification
4. Similarities Between Co and Post Translational Modification
5. Side by Side Comparison – Co vs Post Translational Modification in Tabular Form
6. Summary

What is Co Translational Modification?

Co translational modifications are a type of protein modifications that take place during translation. Therefore, these modifications happen during protein synthesis. Co-translational modifications mainly occur in RER. Newly synthesizing polypeptides undergo co-translational modifications. Some of the co-translational modifications are regulation of translation, protein folding and processing, myristoylation, prenylation and palmitoylation. N-linked glycosylation is a step involved in protein folding in the RER. Moreover, molecular chaperons in RER facilitate protein folding.

What is a Post Translational Modification?

Post-translational modification is a covalent or enzymatic modification of proteins after translation. Hence, post-translational modifications occur after protein biosynthesis. These modifications take place in several cell organelles such as RER, Golgi body, endosomes, lysosomes and secretory vesicles. Generally, post-translational modifications are structural modifications which increase the functional diversity of the proteins. It happens via the addition of functional groups or proteins, proteolytic cleavage of regulatory subunits or by the degradation of entire proteins.

Examples of post-translational modifications include phosphorylation, glycosylation, ubiquitination, nitrosylation, methylation, acetylation, lipidation and proteolysis. Post-translational modifications are crucial since they influence almost all aspects of cell biology. Mature functional proteins are produced after post-translational modifications in the cell. They increase the complexity of the proteome within a cell. Also, post-translational modifications are critical in the study of cell biology and disease treatment and prevention.

What are the Similarities Between Co and Post Translational Modification?

• Co and post-translational modifications are two of the three levels of protein modifications.
• Both types are structural modifications.
• They take place during and after translation.
• They are critical for generating a stable protein structure and appropriate function.
• Both co and post-translational modifications take place in RER.

What is the Difference Between Co and Post Translational Modification?

Co-translational modification is a type of protein modification which happens during the translation while the post-translational modification is a type of protein modification which happens after translation. Thus, this is the key difference between co and post translational modification.  Co translational modifications happen mainly in the RER while post-translational modifications happen in different organelles including RER, Golgi, endosomes, lysosomes and secretory vesicles.

Moreover, regulation of translation, protein folding and processing, myristoylation, prenylation and palmitoylation are several co-translational modifications while phosphorylation, glycosylation, ubiquitination, nitrosylation, methylation, acetylation, lipidation and proteolysis are several post-translational modifications.

Below is a summary of the difference between co and post translational modification in tabular form.

Summary – Co vs Post Translational Modification

Protein modifications are critical for generating stable protein structure and ultimately appropriate function. Co and post-translational modifications are two such protein modifications. Co-translational modifications occur during translation. These modifications happen in the rough endoplasmic reticulum. But, post-translational modifications take place after the translation or biosynthesis of proteins. They take place in several different cell organelles including, RER, Golgi bodies, lysosomes, endosomes and secretory vesicles, etc. Post-translational modifications increase proteomic diversity influencing all most all aspects of cell biology. Thus, these are the main differences between co and post-translational modification.

Reference:

1. Shandala, Tetyana, et al. “Protein: Cotranslational and Posttranslational Modification in Organelles.” Wiley Online Library, American Cancer Society, 17 Jan. 2011, Available here.
2. “Overview of Post-Translational Modification: Thermo Fisher Scientific – US.” Overview of Post-Translational Modification | Thermo Fisher Scientific – US, Available here.

Image Courtesy:

1. “MiRNA mechanisms” By A. Zinovyev, N. Morozova, A. N. Gorban, A. Harel-Belan – Mathematical modeling of microRNA-mediated mechanisms of translation repression, arXiv:1202.1243v2 [q-bio.MN] (CC BY 3.0) via Commons Wikimedia

2.  “Post-translational modification by cleavage” By Kep17 – Own work (CC BY-SA 4.0) via Commons Wikimedia