Fig. 6: Interaction of hANP32A with full-length FluB polymerase.

a Chemical shifts of ¹⁵N-labelled IDD of hANP32A (4 μM) upon addition of full-length FluB polymerase (32 μM) bound to viral promoter RNA (vRNA). Measurement at 850 MHz, 293 K. Red—free protein, blue—in presence of polymerase. Notably the distribution of chemical shifts is highly similar to that induced in hANP32A upon addition of IAV 627-NLS(K). b CSP associated with a. c Intensity ratio of ¹⁵N-labelled full-length hANP32A (4 μM) upon addition of full-length FluB polymerase (32 μM) bound to vRNA. d Compatibility of the experimentally observed binding mode in the context of the vRNA-bound conformation of FluB polymerase²⁶. The 627 domain was superimposed on the 627 domain of PB2 in the full-length polymerase structure (4wsa). In this position, ANP32A LRR can be accommodated in a large pocket formed by 627 (yellow–orange), and cap-binding domains of PB2 (yellow) and bordered by PB1 (dark-cyan). Inset: PB2 adaptive mutants D521 and K355 lie in the immediate vicinity of ANP32A LRR. e Conformational sampling of the IDD of hANP32A, assuming the position of the LRR of ANP32A shown in d. The linker and NLS domains are not shown for clarity and are assumed flexible. f Conformational sampling of the IDD of avANP32A (otherwise as in e). g Compatibility of the experimentally observed binding mode in the context of the cRNA-bound conformation of FluB²⁹. The 627 domain was superimposed on the 627 domain of PB2 in the full-length polymerase structure (5epi), which is dislocated relative to the vRNA-bound form. ANP32A LRR can be accommodated easily on the accessible surface of 627. The NLS domain (brick red) is detached from 627 in this structure. h Conformational sampling of the IDD of hANP32A, assuming the position of the LRR of ANP32A shown in g. Sampling of the IDD (light blue) linker and NLS domains are shown (brick red).