This suggests that the hupW proteases are under the same or selleckchem similar transcriptional regulation Selleck Selonsertib as the hydrogenases they cleave. This expression pattern could be explained by the putative NtcA binding sites in the promoter region of hupW in both Nostoc punctiforme and Nostoc PCC 7120 (Figure 3b). NtcA binding sites have been found upstream of hupSL in Gloeothece sp. ATCC 27152 [44], Nostoc punctiforme [45], Lyngbya majuscule CCAP 1446/4 [46] and Anabaena variabilis ATCC 29413 [47], and putative binding sites have been observed upstream of the hyp-genes in Nostoc punctiforme [48]. The two putative NtcA binding
sites (TGAN8CAC and GTAN12TAC) identified upstream of the TSP of hupW in Nostoc PCC 7120
are imperfect when compared with the sequence signature of NtcA (GTAN8TAC) [49, 50]. These sites are therefore likely to have none or a very weak binding affinity to NtcA and the two conserved regions observed downstream of the TSP may be the target of additional transcription factors. Sequences similar to these conserved regions CH5183284 manufacturer were also found in the intergenic regions of several other genes in Nostoc PCC 7120 and Anabaena variabilis ATCC 29413 (data not shown) and one of the conserved regions shows resemblance to an IHF binding site and the consensus sequence WATCAANNNNTTR [26, 51]. Binding sites for IHF have previously been found in the promoter region of hupSL in Nostoc punctiforme [45] and Lyngbya majuscula [46] but have also been observed upstream of the hup genes in Bradyrhizobium japonicum [52], the nif genes in purple bacteria [53] and the nif operon in Anabaena azollae [54]. Transciptional studies of hoxW in Nostoc sp
strain PCC 7120 Contrary to the hupW regulation, the result from the Northern blot studies of transcript level on hoxW in Nostoc PCC 7120 showed only a minor difference between non N2-fixing (lower) and N2-fixing conditions (higher). Considering the very small difference seen in transcript level the main function of the bi-directional Teicoplanin hydrogenase and its specific protease indicate that it is not connected to N2-fixation. Studies of the transcript levels of the bi-directional hydrogenase subunit hoxH, when shifted from non N2-fixing to N2-fixing (Nostoc muscorum) or to N2 limiting (Gloeocapsa alpicola) conditions, shows either no effect (Nostoc; [20]) or very small effect (Gloeocapsa; [55]). However further studies of the bi-directional hydrogenase activity in Gloeocapsa alpicola actually showed significantly increased activity even though the relative abundance of hoxH (and hoxY) transcript did not change [55]. Conserved regions were identified in the promoter region of hoxW.