Conserved flanking sequences region

Inducible NOS is active as a homodimer of approximately 260 kDa and only the dimeric forms exhibit catalytic activity. The expression of iNOS is regulated both at the level of transcription and at the level of iNOS mRNA stability. The mechanism of iNOS induction involves de novo ttanscription and biosynthesis of new protein. The 5 -flanking region of murine and human iNOS shares a 66% homology and contains conserved consensus sequences for nuclear factor kappa-B (NF-kB) as well as both INF-Y-/TNF-responsive elements (Chartrain et al. 1994). 

Sirtuins have been conserved from bacteria to eukaryotes. Notably, they all possess a conserved catalytic core domain flanked by sequence-divergent N- and C-terminal regions. If bacteria and archaebacteria generally possess one or two sirtuins, this number is higher in eukaryotes, with five sirtuins in Saccharomyces cerevisiae and seven in human. The presence of sirtuins in all phyla of life led to a wealth of structural data, not only on eukaryotic enzymes but also on bacterial and archaebacteria enzymes. 

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