Methionine—tRNA ligase

Methionine—tRNA ligase is an enzyme that plays a crucial role in the process of protein biosynthesis. It is responsible for attaching the amino acid methionine to its corresponding tRNA molecule, a process known as aminoacylation. This enzyme is classified under the aminoacyl-tRNA synthetases, a group of enzymes that are essential for the translation of the genetic code into proteins.

Function

Methionine—tRNA ligase catalyzes the esterification of methionine to its cognate tRNA, specifically tRNA^Met. This reaction is a two-step process:

1. The enzyme first activates methionine by forming a methionyl-adenylate intermediate, using ATP.
2. The activated methionine is then transferred to the 3' end of the tRNA^Met, forming methionyl-tRNA^Met.

This charged tRNA is then ready to participate in the initiation of protein synthesis on the ribosome.

Structure

Methionine—tRNA ligase is a complex protein that typically consists of multiple domains. These domains are responsible for binding ATP, methionine, and tRNA. The enzyme's structure allows it to recognize and bind specifically to its substrate tRNA^Met, ensuring high fidelity in protein synthesis.

Biological Importance

The enzyme is vital for the initiation of protein synthesis, as methionine is the first amino acid incorporated into nascent polypeptides in eukaryotes and archaea. In bacteria, a modified form of methionine, N-formylmethionine, is used for initiation. Methionine—tRNA ligase ensures that methionine is correctly attached to tRNA^Met, which is crucial for the accurate translation of mRNA into proteins.

Related pages

• Aminoacyl-tRNA synthetase
• Protein biosynthesis
• Transfer RNA
• Methionine

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