Extended Data Fig. 8: Biophysical analysis of HTLV-1 and HIV-1 CA constructs.
From: Distinct stabilization of the human T cell leukemia virus type 1 immature Gag lattice
Biophysical analysis of HTLV-1 (panels a-c) and HIV-1 (panels d-f) CA and their N-terminal and C-terminal domains. Measurements are always performed in two conditions, termed pre-assembly (left side of respective panel) and post-assembly (right side of respective panel). a,d) First derivative of the fluorescence ratio over a temperature ramp, measured by nanoDSF, for HTLV-1 (a) and HIV-1 (d) CA (green), CA-NTD (cyan), and CA-CTD (orange) in pre-assembly and post-assembly conditions. Both full-length HTLV-1 CA and HTLV-1 CA-NTD show a drop in Tm upon assembly. This drop in Tm might reflect the changed reactivity of CA and CA-NTD in assembly conditions. Buffer conditions selected for assembly are chosen to stimulate protein-protein interactions (for example rendering the proteins to be more assembly reactive). This could make them more dynamic and also flexible in order to allow forming such interactions. Virus assembly is not necessarily representing a stable end state, as viruses need to be metastable to eventually release the viral genome. A Tm drop might therefore reflect the propensity of the proteins to allow assembly and disassembly. b,e) Turbidity change as a function of temperature, measured by back-reflection, for HTLV-1 (b) and HIV-1 (e) CA, CA-NTD, and CA-CTD in pre-assembly and post-assembly conditions. Tm for all constructs as well as the turbidity inflection points are given in Supplementary Table 2. c,f) Cumulant radius over a temperature ramp, measured by DLS, for HTLV-1 (c) and HIV-1 (f) CA, CA-NTD, and CA-CTD in pre-assembly and post-assembly conditions. CA and CA-NTD show an increase in cumulant radius coinciding with the observed turbidity increase and respective melting temperatures. CA-CTD shows no significant cumulant radius increase across all conditions. The color code is indicated on the bottom of the figure. The shown data is from one biological replicate measured three times, and representative for all three replicates performed at least three times. Data for the fluorescence ratio and turbidity measurements are presented as mean values +/- standard deviation and for the cumulant radius as mean values with smoothed curve using a Savitzky-Golay filter with a 5-point window and 0-order polynomial. Source data is provided alongside the manuscript.
