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1.4 Protein tertiary structure

The term ‘tertiary structure’ when applied to a protein refers to the three-dimensional arrangement of the polypeptide as a whole, i.e. the spatial relationship between its elements of secondary structure. Though it may not be immediately obvious, proteins do follow certain recognisable folding patterns.

Examination of protein structures resolved by X-ray diffraction and NMR has revealed a variety of folding patterns common to many different proteins. However, even within these folds, distinct substructures or structural motifs, i.e. distinctive arrangements of elements of secondary structure, have been described. The term supersecondary structure has been coined to describe this level of organisation, which is intermediate between secondary and tertiary. The observation that these motifs and protein folds occur in many different proteins, with quite distinct amino acid sequences, indicates that they are not strictly sequence-dependent. Nonetheless, the chemical nature of the component residues (charged, polar or non-polar) is critical in many cases, and your attention is drawn to these.


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