One of the most prevalent sexually transmitted diseases is caused by the bacteri
ID: 211559 • Letter: O
Question
One of the most prevalent sexually transmitted diseases is caused by the bacterium Chlamydia trachomatis and leads to blindness if left untreated. Upon infection, metabolically inert cells differentiate, through gene expression, to become metabolically active cells that divide by binary fission. It has been proposed that release from the inert state is dependent on heat-shock proteins that both activate the reproductive cycle and facilitate the binding of chlamydiae to host cells.
Researchers (Wilson & Tan, 2002) made the following observations regarding the heat-shock regulatory system in Chlamydia trachomatis:
Based on this information, which of the following might explain the heat-dependent regulation of metabolism in Chlamydia trachomatis ?
Some bacteria, like E. coli, use a heat-shock sigma factor to regulate heat-shock transcription. Are the above findings in Chlamydia compatible with use of a heat-sensitive sigma factor? Yes or no?
(1) A regulator protein (call it R) binds to a cis-acting DNA element (call it D). (2) R and D function as a repressor-operator pair. (3) R functions as a negative regulator of transcription. (4) D is composed of an inverted-repeat sequence. (5) Repression by R is dependent on D being supercoiled.Explanation / Answer
the heat-dependent regulation of metabolism in Chlamydia trachomatis can be explained by the changes made by Heat in the shape(conformation) of R and prevents R from binding to D. Transcription is stimulated by heat shock.
the above findings in Chlamydia are not compatible with the use of heat sensitive sigma factor as a sigma factor is formed by E.Coli in heat stress which is required to activate the expression of specific heat shock genes which encode proteins that will protect cells from several kinds of heat-induced damage. the sigma factor changes the promoter recognition of the RNA Polymerase core enzyme. this factor specifically recognizes promoters that contain G-C rich sequences at the -10 position rather than the usual A-T rich sequence of the Pribnow box.
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