Ubiquitin-like proteins play important roles in diverse biological processes.
In Mycobacterium tuberculosis, Pup (prokaryotic ubiquitin-like protein), a
functional homologue of eukaryotic ubiquitin, interacts with the proteasome ATPase
subunit Mpa to recognize and unfold substrates, and then translocate them
into the proteasome core for degradation. Previous studies revealed that, Pup, an
intrinsically disordered protein (IDP), adopts a helical structure upon binding to
the N-terminal coiled-coil domain of Mpa, at its disordered C-terminal region. In
the present study, using circular dichroism (CD), surface plasmon resonance (SPR)
and nuclear magnetic resonance (NMR), we show that membrane mimetic and
acidic conditions also induce Pup to adopt helical conformations. Moreover, at low
pH, Pup, via both of its N- and C-terminal regions, binds to Mpa on sites from the N-terminal region
in addition to the C-terminal region of the coiled-coil domain. Our results imply Pup may play undiscovered
roles in some biological processes e.g. those involve in membrane.