The role of local tight packing of hydrophobic groups in beta-structure.

An analysis of the tendency of hydrophobic groups to tight packing on the surface of beta-sheets based on well-known parameters of beta-sheets and hydrophobic groups was conducted. This analysis shows the existence of very limited numbers and clearly outlined architecture families of regular parts for the majority of beta-structure-containing domains. Each family of architecture strongly depends on the number of beta-strands in the pure beta-domains and on the existence and number of additional alpha-helixes and on the mutual arrangements beta-strands and alpha-helixes along the chain in mixed alpha/beta-domains. This paper demonstrates that the tendency of hydrophobic groups to the local tight packing on the surface of beta-sheets is probably the main reason for the twist of beta-sheets.