A beta strand is an element of secondary structure in which the protein chain is nearly linear. Adjacent beta strands can hydrogen bond to form a beta sheet (also referred to as a beta pleated sheet). The participating beta strands are not continuous in the primary sequence, and do not even have to be close to each other in the sequence, i.e. the strands forming a beta sheet can be separated in primary structure by long sequences of amino acids that are not part of the sheet. Approximately a quarter of all residues in a typical protein are in beta strands, though this varies greatly between proteins. In a parallel beta-sheet, all bonded strands have the same N to C direction. As a result they have to be separated by long sequence stretches. The hydrogen bonds are equally distanced. In an antiparallel beta-sheet, the beta strands run in alternating directions and therefore can be quite close on the primary sequence. The distance between successive hydrogen bonds alternates between shorter and longer. Here you can see an example of a parallel beta-sheet structure, exemplified by the crystal structure of a bacterial alginate epimerase/lyase (PDB code: 8XFR)

#molecularart #betasheet #betastrand #parallel #epimerase

Structure rendered with @proteinimaging, post-processed with @stylar.ai_official and depicted with @corelphotopaint