Question

Suggest a reason why the amino acids thyroxine and hydroxyproline are produced by postranslational modification of the amino acids tyrosine and proline, respectively.

Short answer

Post-translational modifications provide thyroxine and hydroxyproline with the necessary chemical properties to perform essential roles like metabolism regulation and collagen stability.

Step-by-step solution

Understand Post-Translational Modification

Post-translational modification refers to the chemical alterations that proteins undergo after they are synthesized. These modifications can affect the protein's function, localization, and overall activity within the cell.

Identify Parent Amino Acids

In this exercise, identify thyroxine and hydroxyproline as modified versions of the amino acids tyrosine and proline, respectively.

Explore the Role of Thyroxine

Thyroxine, also known as T4, is synthesized from tyrosine and plays a crucial role as a thyroid hormone. Thyroxine affects metabolism, heart rate, and body temperature.

Explore the Role of Hydroxyproline

Hydroxyproline, a modification of proline, is particularly important in the stability of collagen, a major structural protein in connective tissues. Hydroxylation of proline allows for hydrogen bonding which stabilizes the collagen triple helix.

Connect Modification to Function

The synthesis of thyroxine and hydroxyproline from tyrosine and proline adds functionality that is critical for the specific roles they play in biological processes. Thyroxine's iodine atoms and hydroxyproline's hydroxyl group are essential for their respective functions.

Conclude the Reason for Modification

The post-translational modification of these amino acids ensures that they can fulfill their essential biological roles effectively. By altering tyrosine and proline, the body can produce specialized molecules with important physiological functions.

Key concepts

amino acids

Amino acids are the building blocks of proteins. They are organic compounds composed of an amino group, a carboxyl group, and a unique side chain. There are 20 standard amino acids, each playing a critical role in protein synthesis and function. Post-translational modifications can alter amino acids, creating specialized molecules crucial for various biological functions.

For example, thyroxine is derived from tyrosine, and hydroxyproline is derived from proline. These modifications allow proteins to perform a wider range of functions and adapt to different cellular environments.

protein function

Proteins perform a multitude of functions in biological systems, from catalyzing biochemical reactions to providing structural support. Their function is largely determined by their primary structure (sequence of amino acids) and the subsequent folding into higher-order structures.

Post-translational modifications play a significant role in defining and expanding protein function. By chemically modifying specific amino acids, proteins gain new capabilities and specificities. For instance, the hydroxylation of proline to hydroxyproline is crucial for the stability of collagen, impacting tissue strength and integrity.

thyroxine

Thyroxine, also known as T4, is a thyroid hormone synthesized from the amino acid tyrosine. It contains iodine atoms, which are essential for its biological activity. Thyroxine regulates various metabolic processes, including heart rate, body temperature, and metabolic rate.

Its production via post-translational modification allows the body to precisely control thyroid hormone levels, ensuring optimal physiological function. The importance of thyroxine underscores the significance of amino acid modifications in maintaining health and homeostasis.

hydroxyproline

Hydroxyproline is a major component of collagen, a structural protein in connective tissues. It is formed by the hydroxylation of proline, a post-translational modification that introduces a hydroxyl group into the proline residue.

This modification enhances collagen's ability to form hydrogen bonds, stabilizing its triple-helix structure. The presence of hydroxyproline is crucial for maintaining the strength and stability of tissues such as skin, tendons, and cartilage, highlighting its significance in biological systems.

tyrosine

Tyrosine is a non-essential amino acid that serves as a precursor to several important molecules, including neurotransmitters and hormones. One of its key roles is in the synthesis of thyroxine, a critical thyroid hormone.

The conversion of tyrosine to thyroxine involves iodination and additional modifications, enabling thyroxine to perform its regulatory functions in metabolism and energy balance. This process exemplifies how post-translational modifications extend the functionality of simple amino acids.

proline

Proline is an amino acid prominent for its role in protein structure, especially in collagen. It has a unique cyclic structure that induces a kink in the protein chain, contributing to the stability of proteins.

When proline is converted to hydroxyproline through hydroxylation, it further stabilizes collagen by facilitating hydrogen bonding. This modification is critical for the mechanical properties of connective tissues, illustrating how slight chemical changes can have significant physiological impacts.

collagen stability

Collagen is a primary structural protein in connective tissues, providing strength and flexibility. The stability of collagen is heavily dependent on the presence of hydroxyproline, which is formed from proline.

Hydroxyproline allows collagen molecules to form stable, triple-helix structures through hydrogen bonding. This stability is essential for the durability and resilience of tissues like skin, bones, and tendons. Post-translational modifications, therefore, play a vital role in maintaining the integrity and functionality of the body's structural proteins.