CII is a very unstable protein in E. coli; it is degraded by a specific protease called FtsH (HflB), encoded by the hfl gene. 

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#Id: 761

#Unit 3. Fundamental Processes

Sigma factor ensures that bacterial RNA polymerase initiates transcription from specific sites, also reduces binding to nonspecific sequences.

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#Id: 5566

#Unit 7. System Physiology – Animal

Assume first a condition in which osmolality is 300 mOsm/kg of H2O throughout the descending and ascending limbs & medullary interstitium

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#Id: 7077

#Unit 3. Fundamental Processes

ThrRS has the opposite problem: It must synthesize Thr–tRNAThr but not Val–tRNAThr. Specificity is conferred by the aminoacylation site, which contains a Zn2+ ion that is coordinated by the side chain OH group of threonine. Valine cannot coordinate the Zn2+ in this way and hence does not undergo adenylylation by ThrRS.  A separate editing site deals with misacylated Ser–tRNAThr. TyrRS distinguishes between tyrosine and phenylalanine through hydrogen missing from the repertoire are GlnRS and asparaginyl-tRNA synthetase (AsnRS). To synthesize Gln-tRNAGln and Asn-tRNAAsn, these organisms possess distinct glutamyl-tRNA synthetase (GluRS) and aspartyl-tRNA synthetase (AspRS) enzymes that are nondiscriminating (ND). GluRSND synthesizes both Glu-tRNAGlu as well as misacylated Glu-tRNAGln; AspRSND synthesizes both Asp-tRNAAsp and misacylated Asp-tRNAAsn.

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#Id: 6466

#Unit 3. Fundamental Processes

Eukaryotic transcription is most often under positive regulation: A transcription factor is provided under tissue-specific control to activate a promoter or set of promoters that contain a common target sequence.

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#Id: 5819

#Unit 7. System Physiology – Animal

The renal epithelial cells express the enzyme 11β-HSD2, which prevent cortisol from activating mineralocorticoid receptors.