Proteopedia:Demo1

The term "motif" when used in structural biology tends to refer to one of two cases:

1. A particular amino-acid sequence that characterises a biochemical function.
2. A set of secondary structure elements that defines a functional or structural role.

There are a great number of protein sequence motifs identified, many of which have well defined structural or functional roles. One such example is the so-called zinc finger motif which is readily identified from the following consensus sequence pattern (where "X" represents any amino acid):

Cys - X_(2-4) - Cys - X₍₃₎ - Phe - X₍₅₎ - Leu - X₍₂₎ - His - X₍₃₎ - His

Coordination of the zinc ion by 4 amino acid residues forces a particular folding of the protein backbone, giving rise to the nickname zinc finger:

The example structure, displayed to the right, that serves to is that of Zif268 protein-DNA complex from Mus musculus. In this example (a C2H2 class zinc finger) the conserved and residues form ligands to a whose coordination is essential to stabilise the tertiary fold of the protein. The fold is important because it helps orientate the to bind to the .

You can watch an explanation in this video: