Fluorescence spectra of TNP-ATP bound to M. leprae HSP18.

(A) Fluorescence emission spectra of TNP-ATP alone (trace 1); TNP-ATP+HSP18 (trace 2); Addition of 0.25 mM ATP to the HSP18-TNP-ATP complex (trace 3). Protein concentration used was 2.5 μM and TNP-ATP concentration was 2.5 μM. Excitation wavelength used was 403 nm and fluorescence emission spectra were recorded from 500–600 nm. (B) Fluorescence titration of 2.5 μM M. leprae HSP18 was carried with varying concentration of TNP-ATP with fluorescence monitored at λ_exc = 403 nm and λ_em = 538 nm.