Glycosylation of Threonine of the Repeating Unit of RNA Polymerase II with β-Linked N-Acetylglucosame Leads to a Turnlike Structure

Two models of the repeating C-terminal domain of RNA polymerase II (Ac−SYSPTSPSYS−NH₂; Ac−SYSPT(β-O-GlcNAc)SPSYS−NH₂) were prepared and their conformations in water studied using 1-D and 2-D ¹H NMR spectroscopies, CD spectrophotometry, fluorescence anisotropy, and molecular mechanics and dynamics calculations. The data suggest that glycosylation of the native, randomly coiled peptide with a single, biologically relevant sugar leads to the formation of a turn. This report represents the first structural study of a new class of glycoproteins monoglycosylated with N-acetylglucosamine on threonine.