Crystal structure of human 5'-deoxy-5'-methylthioadenosine phosphorylase in complex with (3R,4S)-1-((4-amino-5H-pyrrolo[3,2-d]pyrimidin-7-yl)methyl)-4-(((3-(1-benzyl-1H-1,2,3-triazol-4-yl)propyl)thio)methyl)pyrrolidin-3-ol