The ST staple is a common four- or five-

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

residue

motif Motif may refer to: General concepts * Motif (chess composition), an element of a move in the consideration of its purpose * Motif (folkloristics), a recurring element that creates recognizable patterns in folklore and folk-art traditions * Moti ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

s and

polypeptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

s with

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...

threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated −COO� ...

as the C-terminal residue. It is characterized by a single hydrogen bond between the hydroxyl group of the

(at residue ''i'' + 3 or ''i'' + 4) and the main chain

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containin ...

group of residue ''i''. Motifs are of two types, depending whether the motif has 4 or 5 residues. Most ST staples occur in conjunction with an

alpha helix The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues e ...

, and are usually associated with a slight bend in the helix. Two websites are available for finding and examining ST staples in proteins:
Motivated Proteins
an
PDBeMotif
{{cite journal, last=Golovin, first=A, author2=Henrick K, title=MSDmotif: exploring protein sites and motifs., journal=BMC Bioinformatics, year=2008, volume=9, pages=312, doi=10.1186/1471-2105-9-312, pmid=18637174, pmc=2491636, issue=1

References

Protein structural motifs Pentapeptides