An unopened knot protein: YbeA

YbeA is one of the methyltransferase which contains deep embedded trefoil knot in its backbone structure. It is challenge to observe the knot transitions during the protein folding process. In this study, the conformation rigidity of YbeA folding intermediates were analyzed by trypsin digested matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectrometry technique. We find that the knotted domain is the most stable region in the entirety structure of YbeA, both in unfolded and folded state. By using fluorescence resonance energy transfer (FRET) measurement, we find that the knot structure remains intact both in unfolded and refolded states. Therefore, we summarized that knot conformation is formed during its translational process and this unique structure becomes an unopened knot. This unique knot structure may facilitate cell to against stress of environment change.