Proteinsynthesizing

Proteinsynthesizing, more commonly referred to as protein synthesis, is the cellular process by which cells generate proteins based on genetic information carried by messenger RNA (mRNA). It consists of transcription of DNA into mRNA and translation of mRNA into a polypeptide, followed by folding and post-translational modification to attain a functional protein.

Transcription occurs in the nucleus in eukaryotes, where a gene is copied into an mRNA transcript with processing steps such as 5' capping, 3' polyadenylation, and splicing to remove introns. The mature mRNA is exported to the cytoplasm. Translation occurs on ribosomes, which may be free or associated with the rough endoplasmic reticulum. In translation, initiation involves the small ribosomal subunit assembling with initiation factors at the start codon (usually AUG). The large subunit joins to form the complete ribosome. During elongation, tRNA molecules bring amino acids matching codons, and the ribosome catalyzes peptide bond formation. The ribosome advances codon by codon until a stop codon terminates translation, releasing the finished polypeptide. GTP hydrolysis provides energy for initiation, elongation, and termination.

After synthesis, the polypeptide folds into its three-dimensional structure with the help of chaperones. Many proteins undergo post-translational modifications such as cleavage, folding, disulfide bond formation, phosphorylation, glycosylation, or targeting to organelles or membranes. Quality control mechanisms detect misfolded proteins for refolding or degradation via proteasomes.

Regulation of protein synthesis occurs at transcriptional, translational, and post-translational levels and is essential for development, metabolism, and response to environmental cues.