Three-dimensional model of the 5e RNA binding fragment of human SRP72. a. Ribbon representation of the three-dimensionaI model of the complete human SRP72 as predicted by I-TASSER  and modified as described in Methods. The N- and C-termini are indicated and the atoms of the residues in RNA binding region (532 to 590) are shown as spheres and colored by charge. b. Closeup of the SRP72 RNA binding domain with the identified minimal region required for forming a complex with the 5e SRP RNA in a surface representation. The conserved tryptophan residue located inside the model is drawn in more detail. Shown are the locations of some lysine residues, the prominent chymotryptic cleavage site (CT585/6) and the tyrosine at position 566. c. Same as panel b but viewed at an approximately 90 degree rotation around the y axis revealing a pocket suitable for binding to the kinked 5e SRP RNA (red).