BioNMR - Long-range effects of tag sequence on marginally stabilized structure in HIV-1 p24 capsid protein monitored using NMR

Long-range effects of tag sequence on marginally stabilized structure in HIV-1 p24 capsid protein monitored using NMR

Publication date: Available online 21 June 2014
Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics
Author(s): Honoka Okazaki , Chie Kaneko , Miyuki Hirahara , Satoru Watanabe , Naoya Tochio , Takanori Kigawa , Chiaki Nishimura
N-terminal domain of HIV-1 p24 capsid protein is a globular fold composed of seven helices and two ?-strands with a flexible structure including the ?4-5 loop and both N- and C-terminal ends. However, the protein shows a high tendency (48%) for an intrinsically disordered structure based on the PONDR VL-XT prediction from the primary sequence. To assess the possibility of marginally stabilized structure under physiological conditions, the N-terminal domain of p24 was destabilized by the addition of an artificial flexible tag to either N- or C-terminal ends, and it was analyzed using T1, T2, hetero-nuclear NOE, and amide-proton exchange experiments. When the C-terminal tag (12 residues) was attached, the regions of the ?3-4 loop and helix 6 as well as the ?4-5 loop attained the flexible structures. Furthermore, in the protein containing the N-terminal tag (27 residues), helix 4 in addition to above-mentioned area including ?3-4 and ?4-5 loops as well as helix 6 exhibited highly disordered structures. Thus, the long-range effects of the existence of tag sequence was observed in the stepwise manner of the appearance of disordered structures (step 1: ?4-5 loop, step 2: ?3-4 loop and helix 6, and step 3: helix 4). Furthermore, the disordered regions in tagged proteins were consistent with the PONDR VL-XT disordered prediction. The dynamic structure located in the middle part (?3-4 loop to helix 6) of the protein shown in this study may be related to the assembly of the viral particle.



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