Multimerization of HIV-1 integrase hinges on conserved SH3-docking platforms

Meytal Galilee; Akram Alian

The inhibitory effect of CTD, as part of the CCDCTD, was diminished upon separating the CTD segment (residues 210-288) and supplementing it to the CCD protein in the reaction mixture ( Figure 4A , CCD/CTD). Furthermore, the addition of CTD to a reaction containing the separate CCD and NTD (residues 1-55), which by itself ( Figure 4A , CCD/NTD) was found more than 3 folds superior to full-length or conjugate NTDCCD, resulted in a significant 33% inhibition ( Figure 4A , CCD/NTD/CTD). Therefore, while NTD positively interferes with the CCD in the 3'-processing activity, the CTD appears to have a negative effect. The contribution of the NTD appears necessary to support appropriate CTD interactions with the CCD. Structural analysis shows that the NTD linker segment (residues 50-58) contributes 55% (725 Ã… 2 ) of the total 1310 Ã… 2 buried CCD/CTD area at site-2 ( Figure 4B) . Interestingly, the carbonyl oxygen of Val54 of NTD linker forms a hydrogen bond (2.91 Ã…) with the side chain of CTD Arg228 (NH2) (Figure 4B ), mutating of which to Arg228Ala resulted in defective HIV-1 viruses (23) . The side chain of NTD Gln53 (NE2) forms a hydrogen bond (2.50 Ã…) with the carbonyl oxygen of CTD Asp229 (Figure 4B) , and also interacts with the side chain of Lys264 (3.6 Ã…). Both Lys264 and Lys266, which hydrogen bond to Ala80, have been shown to play an important role in the LEDGINs induced aberrant multimerization (27) . Indeed, the fundamental role of CTD . CC-BY 4.0 International license author/funder. It is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/301721 doi: bioRxiv preprint in aberrant IN aggregation has previously been emphasized (10, 27, 28) . CTD interactions with the NTD linker (residues 44-53) at site-1, which provides the main docking template for CTD at this site, buries a total of 944 Ã… 2 ( Figure 4C) . Therefore, the NTD linker appears to play a crucial role in modulating the CCD/CTD docking platform and functional IN mutlimerization and is worth exploring in future studies.