Structure of recombinant Thermoascus aurantiacus xylanase TaXyn10 with an authentic N-terminal pyroglutamate.

The thermostable GH10 xylanase from Thermoascus aurantiacus (TaXyn10) is an industrially relevant enzyme whose native structure contains an N-terminal pyroglutamate (PCA) modification. Recombinant production of proteins containing an N-terminal PCA is often hindered by purification strategies that disrupt the authentic N-terminus. Here, we report the 1.1 Å resolution crystal structure of TaXyn10 recombinantly produced in Escherichia coli and purified using a split-intein-based system. The structure closely resembles that of the native protein. Electron-density maps support the presence of an intact N-terminal PCA, with partial occupancy consistent with spontaneous cyclization of the exposed N-terminal glutamine after intein cleavage. These results demonstrate that split-intein-based purification enables recovery of the native mature state of TaXyn10 and can preserve physiologically relevant N-terminal PCA formation in recombinant protein produced in E. coli.