Modeling Beta-Traces for Beta-Barrels from Cryo-EM Density Maps

Cryo-electron microscopy (cryo-EM) has produced density maps of various resolutions. Althoughα-helices can be detected from density maps at 5–8 Å resolutions,β-strands are challenging to detect at such density maps due to close-spacing ofβ-strands. The variety of shapes ofβ-sheets adds the complexity ofβ-strands detection from density maps. We propose a new approach to model traces ofβ-strands forβ-barrel density regions that are extracted from cryo-EM density maps. In the test containing eightβ-barrels extracted from experimental cryo-EM density maps at 5.5 Å–8.25 Å resolution,StrandRollerdetected about 74.26% of the amino acids in theβ-strands with an overall 2.05 Å 2-way distance between the detectedβ-traces and the observed ones, if the best of the fifteen detection cases is considered.