B. Franzetti et al., Characterization of a novel complex from halophilic archaebacteria, which displays chaperone-like activities in vitro, J BIOL CHEM, 276(32), 2001, pp. 29906-29914
We isolated a protein, P45, from the extreme halophilic archaeon Haloarcula
marismortui, which displays molecular chaperone activities in vitro. P45 i
s a weak ATPase that assembles into a large ring-shaped oligomeric complex
comprising about 10 subunits. The protein shows no significant homology to
any known protein. P45 forms complexes with halophilic malate dehydrogenase
during its salt-dependent denaturation/renaturation and decreases the rate
of deactivation of the enzyme in an ATP-dependent manner. Compared with ot
her halophilic proteins, the P45 complex appears to be much less dependent
on salt for its various activities or stability. In vivo experiments showed
that P45 accumulates when cells are exposed to a low salt environment. We
suggest, therefore, that P45 could protect halophilic proteins against dena
turation under conditions of cellular hyposaline stress.