> See also: > - [[Protein]] > - [[Translation]] > - [[Protein Conformational Changes]] > - [[Ribonucleic Acid (RNA)]] # Post-Translational Modifications **Pre-messenger RNA** (*pre-mRNA*), also known as Heterogenous RNA (*hnRNA*), is the immediate product of [[Transcription|transcription]]. A **signal peptide** is specific for the type of secretion system - Found on the N-terminus of polypeptide (at start of translation) ![[Pasted image 20240310155826.png|400]] [[Protein Structure]] Protein Disulfide Isomerase This is a feature unique to eukaryotic cells that is not found in prokaryotic cells. Because of this, bacteria can't be used to produce certain types of proteins, such as antibodies ## The Spliceosome Small nuclear RNA (snRNA) participates in the pre-mRNA splicing reaction ## Molecular Chaperones Cells use proteins called **chaperones** to suppress incorrect folding and in some cases to correct any misfolding that may have occurred. - These are so essential that they can be found in all domains of life ## Ubiquitination **Ubiquitin** is a 76 amino acid protein that can be attached to other proteins, flagging them for degradation, subcellular localization, or kinase activation. - Ubiquitin-Activating Enzyme (E1) - Ubiquitin-Conjugating Enzyme (E2) - Ubiquitin-Ligating Enzyme (E3)