SINTESIS PROTEIN : TRANSLASI

Introduction

This tutorial explains the process of protein synthesis through translation, following transcription. It covers how messenger RNA (mRNA) is used as a template for protein creation and outlines the key steps involved in translation, including the roles of ribosomes and transfer RNA (tRNA).

Step 1: Understanding mRNA and Its Role

• After transcription, mRNA moves from the nucleus to the cytoplasm.
• mRNA serves as a template for protein synthesis, containing sequences of nitrogenous bases grouped into codons (sets of three bases).
• Each codon corresponds to a specific amino acid.

Step 2: Recognizing Pairing Rules

• During translation, specific base pairing occurs between mRNA and tRNA:
  • Adenine (A) on mRNA pairs with Uracil (U) on tRNA.
  • Uracil (U) on mRNA pairs with Adenine (A) on tRNA.
  • Guanine (G) on mRNA pairs with Cytosine (C) on tRNA.
  • Cytosine (C) on mRNA pairs with Guanine (G) on tRNA.

Step 3: Initiation of Translation

• The translation process begins with the small subunit of the ribosome binding to the mRNA.
• The ribosome moves along the mRNA from the 5' to the 3' end.
• It identifies the start codon AUG, which signals the attachment of the tRNA carrying the amino acid methionine (with the anticodon UAC).
• Once the tRNA is attached, the large subunit of the ribosome binds to form a complete ribosome.

Step 4: Structure of the Ribosome

• The ribosome has three critical sites:
  • A site (Aminoacyl site)
  • P site (Peptidyl site)
  • E site (Exit site)

Step 5: Elongation Phase

• During elongation, additional tRNAs bring amino acids to the ribosome, matching their anticodons with the codons on the mRNA.
• Use a codon table to determine which amino acid corresponds to each codon (e.g., AUG = methionine).
• New amino acids enter the A site, and a peptide bond forms between the amino acids in the P site.
• The ribosome then shifts to the next codon, moving the tRNA that has released its amino acid to the E site, preparing it for exit.

Step 6: Termination of Translation

• Termination occurs when a stop codon (UAA, UAG, or UGA) reaches the P site.
• A protein known as the release factor (RF) recognizes the stop codon and enters the A site.
• This causes the polypeptide chain to be released from the ribosome, completing the formation of the protein.
• The ribosome then disassembles, ready to initiate a new translation process.

Conclusion

The translation process is a crucial part of protein synthesis, involving multiple steps and specific interactions between mRNA, tRNA, and ribosomes. Understanding these steps helps in grasping how proteins are formed, which are vital for various cellular functions. For further details, consider exploring supplemental resources or related web content.