Competitive and Cooperative Interactions Mediate RNA Transfer from Herpesvirus Saimiri ORF57 to the Mammalian Export Adaptor ALYREF
Figure 5
Typical effects of complex formation and RNA→protein ST on selected signals of ALYREF1–155 and ORF578–120.
The 1H dimension slices through 1H-15N-correlation spectra are displayed for three representative signals of each protein, on the left for ALYREF and on the right for ORF57. The residue assignments in the free form are labeled at the top, and same signals are shown below each other for different complexes, as indicated. First type of signal (ALYREFM1 and ORF57E24) is not significantly affected by any complex formation, or ST. Second type (ALYREFA34 and ORF57Y81) is not affected much by protein and marginally affected by RNA binding, but is altered or displays significant ST effect in the ternary complex (percentage drop in signal intensity is indicated in blue, and ST spectral traces shown in red). These are residues likely contributing to cooperative ternary complex formation, forming contacts with RNA. Third type of signals originates from the structured regions of proteins (ALYREFA104 and ORF57R111). ALYREFA104 signal is not significantly affected in protein-protein complex, but shows significant increase in ST effect in the ternary complex, suggesting that ORF57 recruits RNA to the proximity of this residue. ORF57R111 signal is broadened beyond detection in protein-protein complex, and remains broadened in the ternary complex. For this signal strong ST effect is observed when in complex with RNA. This residue is involved in initial viral RNA recognition, but then RNA is displaced from this site by ALYREF binding.