Figure 4

PfNapS-histone interaction studies using fluorescence spectroscopy (a). PfNapS dimer is shown as molecular surface. Domains I and II are coloured blue and green respectively. The residues Cys47 and Cys154 are coloured red and yellow and are indicated. (b) Fluorescence emission spectra of PfNapS in presence of increasingconcentrations of histones. A hypsochromic shift (blue shift) was observed onbinding of histones. However in case of histone H1 no such change wasobserved. Fluorescence intensity was measured after incubating75 micro gram of PfNapS protein with 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 micrograms ofhistones. All experiments were repeated thrice. (c) Effect of labeling on binding of PfNapS to histones H3 and H1. (d) Graph representing hypsochromic shift (F460/485) in fluorescence of two PfNapS mutants as a function of amount of H3 histone. (e) Graph representing differential binding of linker histone H1 with respect to core histones. There is no shift in fluorescence on binding of H1, however, core histones show hypsochromic shift (F460/485) in fluorescence.