Singular points of protein β‐sheets

Protein ß‐sheets can be regarded as surfaces. Two surfaces can be connected along a common edge to form a larger surface, or two edges of a surface can coalesce to form a closed sheet such as a ß‐barrel. Singular points are locations where these connections are not perfect. In protein ß‐sheets, a singular point is characterized by a residue separating two ß‐ladders. In this paper, we study the singular points of protein ß‐sheets from the surface topologic viewpoint, summarize our search results from the protein structural data in the Protein Data Bank, and present examples where singular points are near the active sites and may contribute to forming the proper relative positions of catalytic residues.