CryoSeek identification of glycofibrils with diverse compositions and structural assemblies

Abstract

Last year, we reported CryoSeek, a research strategy that employs cryo-electron microscopy (cryo-EM) to discover novel bio-entities from any accessible source, supplemented with AI-facilitated data processing and bioinformatic analyses. Here we report CryoSeek characterization of five additional glycofibrils isolated from the Tsinghua Lotus Pond (TLP), named TLP-IPT, TLP-12, TLP-3, TLP-2, and TLP-0, with overall resolutions ranging from 3.0-3.5 [A]. These five glycofibrils, all covered with dense glycoshells, have decreasing ratios of the central protein components, with TLP-0 with no protein at all. IPT (immunoglobulin-like, plexins, transcription factors) refers to the tandem domain that constitutes the central filament of this type of glycofibrils. In TLP-12, the central cylindrical stem is made of a trimer of dodecapeptide repeats that weave to {beta}-sheet ribbons. The central stem of TLP-3 is also a trimer, but of linear tripeptide repeats. TLP-2, similar to our previously reported TLP-4, only has a linear chain of dipeptide repeats, and glycosylation occurs to a phosphoserine in each repeat. Glycan-mediated interactions are essential for the assembly of all five glycofibrils. Our previous and present studies demonstrate the diversity in the high-order structure and folding of glycans.