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Abstract
In the present study, a stereochemical analysis of proteins containing β-β-hairpins closed into cycles by S-S-bridges has been performed. A database of these proteins has been compiled from the Protein Data Bank (total 428 PDB entries). 390 β-β-hairpins closed into cycles by S-S-bridges have been found in non-homologous proteins included into the database. An alysis showed that 118 hairpins contain S-S-bridges formed by cysteins located opposite to each other in the neighboring β-strands. Among them, 110 hairpins are left-turned and 8 β-hairpins are right-turned when viewed from the same side where S-S-bridges are located. In the other group of 272 β-hairpins, the S-S-bridge is formed by two cysteins one of which is located in the β-strand and the other in the loop juxtaposed to the β-hairpin at the N- (84% cases) or C-terminus ( 16% cases). As shown, in most cases the loop-hairpin region closed into a cycle by the S-S-bridge formed a turn of a left-handed superhelix.[PUBLICATION ABSTRACT]