Superposition of IAPV-IRES models corresponding to IAPV-IRES/40S class 1 and 2 after alignments excluding the IRES and the 40S head. A similar conformation can be observed with distinctive relative orientation with respects to the 40S body. The movements characteristic of the 40S head are indicated by arrows in orthogonal views. Ribbon diagram of the IAPV- IRES colored by pairwise root-mean-square deviation displacements observed between the two IAPV-IRES/40S classes. The ASL/mRNA like regions of the PKI and well as the SL-IV shows the lowest degree of displacement (blue) whereas the apical part of SL-III and the L1.1 the highest (red). 