Glutamine—tRNA ligase

Glutamine—tRNA ligase, also known as glutaminyl-tRNA synthetase (GlnRS), is an enzyme that plays a crucial role in the process of protein synthesis within cells. This enzyme is responsible for attaching the amino acid glutamine to its corresponding transfer RNA (tRNA), a critical step in the translation of genetic code into proteins. Glutamine—tRNA ligase is part of the aminoacyl-tRNA synthetase (aaRS) family, a group of enzymes that are essential for protein biosynthesis.

Function

Glutamine—tRNA ligase catalyzes the esterification of glutamine to its compatible tRNA molecule. This reaction involves the attachment of glutamine to the 3' end of the tRNA, forming glutaminyl-tRNA. This process is vital for the accurate translation of the genetic code into a corresponding protein sequence, as it ensures that glutamine is incorporated at the correct positions according to the mRNA template during protein synthesis.

Mechanism

The enzyme operates through a two-step mechanism:

1. Activation of glutamine by ATP to form glutamyl-AMP and pyrophosphate.
2. Transfer of glutamine from glutamyl-AMP to the specific tRNA, resulting in glutaminyl-tRNA and AMP.

This mechanism ensures high fidelity in protein synthesis, minimizing errors in amino acid incorporation.

Structure

Glutamine—tRNA ligase is characterized by a modular architecture, common to many members of the aminoacyl-tRNA synthetase family. It typically consists of an aminoacylation domain where the activation and transfer of glutamine occur, and additional domains that may be involved in tRNA recognition and binding. The precise structure can vary among different species, reflecting the evolutionary diversity of this enzyme family.

Clinical Significance

Alterations in the function or expression of glutamine—tRNA ligase have been implicated in various human diseases. Given its essential role in protein synthesis, any dysfunction in this enzyme could potentially disrupt cellular homeostasis and lead to disease states. Research into glutamine—tRNA ligase may offer insights into novel therapeutic targets for diseases caused by protein synthesis abnormalities.

Evolution

Glutamine—tRNA ligase belongs to a highly conserved family of enzymes, indicating its fundamental role in cellular biology. The evolutionary conservation of these enzymes underscores their critical function in protein synthesis across all forms of life.

See Also

• Aminoacyl-tRNA synthetase
• Protein synthesis
• Transfer RNA
• Genetic code