Amino Acid Motifs|Amino Acid Sequence|Binding Sites|Enzyme Activation|Molecular Conformation|Protein Binding|Saccharomyces cerevisiae|Saccharomyces cerevisiae Proteins|Sequence Analysis, Protein|Sequence Homology, Amino Acid|Structure-Activity Relationship|Substrate Specificity|Ubiquitin|Ubiquitin-Activating Enzymes