Lindsay Ditlevsen posted an update 1 month, 3 weeks ago
Expression of a cascade of genes coding for enzymes involved in either DNA repair or carbon starvation. A LexA-depleted mutant of Synechocystis sp. 6803 had lower LMI070 hydrogenase activity than the wild kind, indicating that LexA operates as a transcription activator of hox genes in this cyanobacterium (87). The binding internet site of LexA upstream of hoxE of Synechocystis sp. PCC 6803 is, surprisingly, not clear (214). LexA may well bind to a region from bp 198 to 338 from the translational start off point (158), towards the region from bp 592 to 690 bp from the hoxE start out codon (87), or to each regions (159). The two distant LexA binding regions inside the hox promoter could indicate the occurrence of a DNA loop involved in gene transcription (86, 159), which warrants experimental proof. LexA could act as mediator from the redox-responsive regulation of hox gene expression (5). In Synechocystis sp. strain PCC6803, LexA binds as a dimer to 12-bp direct repeats containing a CTAN9CTA sequence in target genes (170). Abr proteins act as transcription elements of antibiotic resistance in organisms apart from cyanobacteria. An AbrB-like protein (sII0359) was recently shown to interact specifically using the promoter area of the hox genes and with its own promoter region (157). Whereas this AbrB-like protein works as a transcription activator in Synechocystis sp. PCC 6803, an additional one of those regulator proteins (sII0822) acts as repressor of the hox gene expression, simply because they have been considerably upregulated in a entirely segregated sII0822 mutant (105). This transcription aspect works in parallel to, but j.1467-9507.2007.00408.x apparently independently from, the long-known nitrogen transcriptional manage element NtcA (97) within the regulation from the expression of genes coding for nitrogen assimilation enzymes (105). The cyanobacterial transcription elements, the LexA- and AbrB-like proteins, show significant divergences in their sequences and functions from the counterpart proteins in other organisms, and their activity could possibly be regulated by posttranscription modifications (159). They may be members of an apparently complicated signal cascade that directs the expression on the bidirectional hydrogenase genes. Their expressions and interactions in responses to environmental cues could possibly be a topic of comprehensive study within the near future (159). The identification of other transcription elements of bidirectional hydrogenase is to be anticipated (116). In addition to its inactivation by O2 in addition to a non-light dependence (51), bidirectional hydrogenase appears to become activated by H2 around the transcriptional or translational level and even on both. The effects of H2 on bidirectional hydrogenase synthesis usually are not understood and appear to differ together with the organism and the culture circumstances employed. In some cases, ece3.1533 higher hydrogenase activity may very well be the outcome of bacterial contamination of slimeforming cyanobacterial cultures. The biosynthesis and maturation with the [NiFe] hydrogenaseBOTHE ET AL.MICROBIOL. MOL. BIOL. REV.FIG. 7. Possible coupling from the bidirectional hydrogenase to the cytoplasmic membrane in cyanobacteria. The HoxE subunit may possibly serve as a device for coupling towards the membrane, but this has not been verified experimentally. Solubilization experiments indicate that 2013/480630 the bidirectional hydrogenase is loosely membrane bound (110).happen to be characterized for the enzyme from E. coli (20). The hyp genes necessary for the synthesis on the hydrogenase are comparable in E.