I think what they mean is that the protein does not have a single conformation that it adopts and then remains in. It's fairly common when solving the x-ray cry

I think what they mean is that the protein does not have a single conformation that it adopts and then remains in. It's fairly common when solving the x-ray crystal structure of a protein to find that some regions of the molecule are just disordered and don't have a clear shape. If you're asking what is going on at the atomic level, the answer would be that the protein is continuously changing shape as it flops around its solution environment. Of course, if you could freeze time at any one instant, you would find that every atom has defined coordinates and therefore the overall molecule has some shape. The point is just that it's dynamic. That's how I interpreted the article, but I don't have any specific knowledge of this protein.