Ser51

Ser51 is a notation used in biochemistry and molecular biology to indicate that the serine amino acid occupies the 51st position in a given protein sequence. It is not a standalone molecule or gene; rather, it describes a residue in the polypeptide chain of a specific protein, where numbering typically starts at the N-terminus. The exact protein and organism must be specified when using "Ser51" to avoid ambiguity (for example, Ser51 in protein X from species Y).

In proteins, serine residues can be sites of catalytic activity, hydrogen bonding, or post-translational modification such as phosphorylation. When researchers study Ser51, they may perform site-directed mutagenesis (for instance substituting alanine or aspartate) to assess its role, or use mass spectrometry to determine whether the residue is modified in vivo. The functional importance of Ser51 is determined by its structural context, neighboring residues, and whether it lies in an active site, a binding interface, or a regulatory motif.

In sequence alignments, conservation of a serine at position 51 across homologs can indicate functional importance, but this must be evaluated per protein family, as numbering differs among sequences and isoforms.

Because "Ser51" is a position-specific descriptor, its meaning is entirely contextual. It should always be interpreted alongside the protein name, organism, and any post-translational modification data. See also serine, residue numbering, and site-directed mutagenesis.