Ser45

Ser45 refers to the serine residue located at position 45 in a given protein sequence. The designation is sequence-specific and depends on the polypeptide’s amino-terminal to carboxyl-terminal numbering, so Ser45 in one protein or isoform may not correspond to the same position in another. Serine residues are common sites for various structural and functional roles, including participation in hydrogen bonding, the formation of local secondary structure, and serving as targets for post-translational modification.

A major context for Ser45 is phosphorylation. Ser45 can be a substrate of serine/threonine kinases, and phosphorylation at this position may influence a protein’s catalytic activity, stability, subcellular localization, or interactions with other molecules. Whether Ser45 is phosphorylated in a particular protein must be demonstrated experimentally, as modification patterns are dynamic and cell-type specific.

When studying Ser45, researchers may use site-directed mutagenesis to substitute serine with alanine (S45A) to block phosphorylation or with aspartate/glutamate (S45D/E) to mimic constitutive phosphorylation. Such mutations help probe the functional importance of this residue in a given protein.

Identification and characterization of Ser45 rely on proteomic and molecular biology methods, including mass spectrometry, peptide mapping, and comparative sequence analysis. Conservation of Ser45 across homologs can indicate structural or functional importance, whereas divergence may reflect species- or context-specific regulation. In any report, Ser45 denotes the serine at position 45 within the specific protein sequence under study.