title: Chains of alternating sulfur and pi-bonded atoms in eight small proteins.
abstract: This paper demonstrates the existence of regions in eight small globular proteins in which the side chains of sulfur-containing amino acids (cysteine and methionine) alternate in space with side chains of aromatic amino acids (histidine, phenylalanine, tryptophan and tyrosine). The proteins are: rubredoxin, high potential iron protein, cytochrome c, flavodoxin, deoxyhemoglobin, trypsin inhibitor, ribonuclease-S, and lysozyme. The sulfur-pi-bonded 'chains' involve a minimum of five and a maximum of 10 amino acids, and contain the most polarizable atoms within proteins. S-pi-chains give extra stability to the folding of proteins; they may also afford paths for the step-wise movement of electrons.
mesh_terms: D000595:Amino Acid Sequence; D003201:Computers; D003574:Cytochrome c Group; D005418:Flavodoxin; D006454:Hemoglobins; D007506:Iron-Sulfur Proteins; D008961:Models, Structural; D009113:Muramidase; D011487:Protein Conformation; D012260:Ribonucleases; D012416:Rubredoxins; D013455:Sulfur; D014361:Trypsin Inhibitors
chemical_list: D003574:Cytochrome c Group; D005418:Flavodoxin; D006454:Hemoglobins; D007506:Iron-Sulfur Proteins; D012416:Rubredoxins; D014361:Trypsin Inhibitors; D013455:Sulfur; D012260:Ribonucleases; D009113:Muramidase