The Covalent Alteration of One or More Amino Acids Occurring in Proteins Peptides and Nascent Polypeptides (co Translational Post Translational Modifications) Occurring At the Level of an Individual Cell. Includes the Modification of Charged Trnas That Are Destined to Occur in a Protein (pre Translation Modification).
A Membrane Bounded Organelle of Eukaryotic Cells in Which Chromosomes Are Housed and Replicated. in Most Cells the Nucleus Contains All of the Cell's Chromosomes Except the Organellar Chromosomes and Is the Site of RNA Synthesis and Processing. in Some Species or in Specialized Cell Types RNA Metabolism or DNA Replication May Be Absent.
Interacting Selectively and Non Covalently with a Nucleotide Any Compound Consisting of a Nucleoside That Is Esterified with (ortho)phosphate or an Oligophosphate At Any Hydroxyl Group On the Ribose or Deoxyribose.
Catalysis of the Reaction: E1 + Ubiquitin + ATP > E1 Ubiquitin + AMP + Ppi Where the E1 Ubiquitin Linkage Is a Thioester Bond Between the C Terminal Glycine of Ub and a Sulfhydryl Side Group of an E1 Cysteine Residue. This Is the First Step in a Cascade of Reactions in Which Ubiquitin Is Ultimately Added to a Protein Substrate.