Department of Structural Biology, Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.|Department of Structural Biology, Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.|Department of Structural Biology, Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.|Department of Structural Biology, Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.|Department of Structural Biology, Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.