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J. Bacteriol., 08 1996, 4484-4492, Vol 178, No. 15
Y Yuan, DD Crane and CE Barry 3rd
The majority of active tuberculosis cases arise as a result of reactivation
of latent organisms which are quiescent within the host. The ability of
mycobacteria to survive extended periods without active replication is a
complex process whose details await elucidation. We used two-dimensional
gel electrophoresis to examine both steady-state protein composition and
time-dependent protein synthetic profiles in aging cultures of virulent
Mycobacterium tuberculosis. At least seven proteins were maximally
synthesized 1 to 2 weeks following the end of log-phase growth. One of
these proteins accumulated to become a predominant stationary-phase
protein. N-terminal amino acid sequencing and immunoreactivity identified
this protein as the 16-kDa alpha- crystallin-like small heat shock protein.
The gene for this protein was shown to be limited to the slowly growing M.
tuberculosis complex of organisms as assessed by Southern blotting.
Overexpression of this protein in wild-type M. tuberculosis resulted in a
slower decline in viability following the end of log-phase growth.
Accumulation of this protein was observed in log-phase cultures following a
shift to oxygen- limiting conditions but not by other external stimuli. The
protein was purified to homogeneity from overexpressing M. smegmatis in two
steps and shown to have a significant ability to suppress the thermal
denaturation of alcohol dehydrogenase. Collectively, these results suggest
that the mycobacterial alpha-crystallin protein may play a role in
enhancing long-term protein stability and therefore long-term survival of
M. tuberculosis.
Copyright © 1996, American Society for Microbiology
Stationary phase-associated protein expression in Mycobacterium tuberculosis: function of the mycobacterial alpha-crystallin homolog
Tuberculosis Research Unit, Laboratory of Intracellular Parasites, National Institutes for Allergy and Infectious Diseases, Rocky Mountain Laboratories, Hamilton, Montana 59840, USA.
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