Some global β‐sheet characterstics

Some Global 8-Sheet CharacteristicsThe 0-pleated sheet has received much attention lately, and a certain understanding of the atomic interactions and geometrical constraints that govern its formation is beginning to emerge.'&Still, the physicochemical basis for the stability of this structure remains to be worked out in detail, and the field is by no means closed.In a recent communication7 we presented data indicating the clear preference of hydrophobic residues to form interstrand nearest-neighbor pairs in &sheets.This conclusion was based on a rather limited protein sample, and with the publication by Levitt and Greers of a comprehensive table of &sheet structures, it was felt that the investigation should be carried further to include this larger data base.Thus, we have analyzed 72 &sheets from Levitt and Greer?comprising 2610 amino acid residues (for similar or closely related proteins only one representative was chosen).The residues were classified as either hydrophobic (Leu, Ile, Phe, Met, Trp, Tyr, Val, Cys), neutral (Ala, Pro, Gly, Thr, Ser), or polar (Am, Gln, Asp, Glu, His, Lys, Arg) and further subdivided into two groups: peripheral (all residues not surrounded on all four sides in the plane of the sheet by nearest neighbors belonging to the sheet) and internal.