Structural Patterns in Globular Proteins

Gail Hutchinson, A. Louise Morris and Janet M. Thornton 

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Levitt, M., Chothia, C. Structural patterns in globular proteins. Nature 261 552-558, 1976. 

The third group of conformations is reverse turns. These are important and common conformational elements in globular proteins that enable the chain to reverse direction and fold back on itself. Proline is often used to cause the structure to reverse direction. Reverse turns can also be stabilized by hydrogen bonding between the first and the third residue. The chain can fold in six different ways to make this hydrogen bond, two of which are like part of a modified a-helix called a 310 helix (310 bends). Some other forms have been called b-bends because the H-bonding pattern resembles that in a b-sheet (Fig. 3.7). 

Secondary structure prediction methods have been complemented by packing analyses of amino acid residues in globular proteins. Packing arrangements have been examined extensively [13, 14] in attempts to identify preferred interaction patterns between non-contiguous amino acid residues. While there is no straightforward way to cast this information into a scheme for prediction of protein structure from sequence, it can certainly be used for plausibility checks on hypothetical protein models or to score protein models obtained by protein folding simulations on lattices [15]. 

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