Phenotype of the rpoD mutant

This mutation causes H. influenzae cells to become competent prematurely, and to reach levels of competence in rich medium that are about 100 times higher than normal cells.  The mutation causes a single amino acid substitution in domain 3 of the 'housekeeping' transcription factor called 'sigma 70'.  rpoD is an essential genes, needed for transcription of most housekeeping genes.  Since the mutant strain (named RR753) shows only a very slight decrease in exponential growth rate we think the mutation causes only a very minor change in the protein's functionMy earlier post this morning said I had never explained my hypothesis about how this mutation causes increased competence, but actually I did, briefly here.  Here's the key sentences from that post:My hypothesis is that the mutation's effect on transcription of sxy mRNA increases competence by increasing sxy translation.   I've long hypothesized that slowing elongation or increasing pausing in the 100 nt segment of sxy mRNA that forms its regulatory secondary structure will promote sxy translation by increasing the ribosome's access to the sxy ribosome-binding site and start codon. Then I listed some low-tech phenotypic analyses that the senior of our two co-op technicians could do:Is RR753 sensitive to the inhibition of competence by added purines?What's the effect of an hfq deletion in this background?How does this strain respond to added...
Source: RRResearch - Category: Medical Scientists Authors: Source Type: blogs