This is the C-terminal domain (CTD) which can be found in murine leukemia virus (MLV) integrase (IN) proteins. The MLV IN C-terminal domain interacts with the bromo and extraterminal (BET) proteins through the ET domain. This interaction provides a structural basis for global in vivo integration-site preferences andt disruption of this interaction through truncation mutations affects the global targeting profile of MLV. The CTD consists an SH3 fold followed by a long unstructured tail [1].

1: Altering murine leukemia virus integration through disruption of the integrase and BET protein family interaction. Aiyer S, Swapna GV, Malani N, Aramini JM, Schneider WM, Plumb MR, Ghanem M, Larue RC, Sharma A, Studamire B, Kvaratskhelia M, Bushman FD, Montelione GT, Roth MJ; Nucleic Acids Res. 2014;42:5917-5928. PMID:24623816

2: A common binding motif in the ET domain of BRD3 forms polymorphic structural interfaces with host and viral proteins. Aiyer S, Swapna GVT, Ma LC, Liu G, Hao J, Chalmers G, Jacobs BC, Montelione GT, Roth MJ; Structure. 2021;29:886-898. PMID:33592170