Hydrogen bonding in globular proteins.
A global census of the hydrogen bonds in 42 X-ray-elucidated proteins was taken and the following demographic trends identified: (1) Most hydrogen bonds are local, i.e. between partners that are close in sequence, the primary exception being hydrogen-bonded ion pairs. (2) Most hydrogen bonds are between backbone atoms in the protein, an average of 68%. (3) All proteins studied have extensive hydrogen-bonded secondary structure, an average of 82%. (4) Almost all backbone hydrogen bonds are within single elements of secondary structure. An approximate rule of thirds applies: slightly more than one-third (37%) form i----i--3 hydrogen bonds, almost one-third (32%) form i----i--4 hydrogen bonds, and slightly less than one-third (26%) reside in paired strands of beta-sheet. The remaining 5% are not wholly within an individual helix, turn or sheet. (5) Side-chain to backbone hydrogen bonds are clustered at helix-capping positions. (6) An extensive network of hydrogen bonds is present in helices. (7) To a close approximation, the total number of hydrogen bonds is a simple function of a protein's helix and sheet content. (8) A unique quantity, termed the reduced number of hydrogen bonds, is defined as the maximum number of hydrogen bonds possible when every donor:acceptor pair is constrained to be 1:1. This quantity scales linearly with chain length, with 0.71 reduced hydrogen bond per residue. Implications of these results for pathways of protein folding are discussed.
Stickle
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DF
Department of Biological Chemistry, Pennsylvania State University College of Medicine, Hershey 17033.
Presta
L G
LG
Dill
K A
KA
Rose
G D
GD
D000465:Algorithms; D000596:Amino Acids / Q000737:chemistry*; D006860:Hydrogen Bonding; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000145:classification; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry; D014961:X-Ray Diffraction
D000596:Amino Acids; D011506:Proteins; D013762:Tetrahydrofolate Dehydrogenase