Sat, 05 Jul 2008 06:23:20 BST CiteULike: cbg's hetr http://www.citeulike.org/user/cbg/tag/hetr CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/cbg/article/2776005 <i>Molecular Microbiology, Vol. 44, No. 5. (2002), pp. 1377-1385.</i><br /><br />Summary Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 depends on both the global nitrogen regulator NtcA and the cell differentiation regulatory protein HetR, and induction of hetR upon nitrogen step-down depends on NtcA. The use of two out of the four transcription start points (tsps) described for the hetR gene (those located at positions -728 and -271) was found to be dependent on NtcA, and the use of the tsp located at position -271 was also dependent on HetR. Thus, autoregulation of hetR could take place via the activation of transcription from this tsp. Expression of ntcA in nitrogen-fixing cultures was higher than in cells growing in the presence of ammonium or nitrate, and high expression of ntcA under nitrogen deficiency resulted from an increased use of tsps located at positions -180 and -49. The induction of the use of these tsps did not take place in ntcA or hetR mutant strains. These results indicate a mutual dependency in the induction of the regulatory genes hetR and ntcA that takes place in response to nitrogen step-down in Anabaena cells. Expression of the hetC gene, which is also involved in the early steps of heterocyst differentiation, from its NtcA-dependent tsp was, however, not dependent on HetR. Mutual dependence of the expression of the cell differentiation regulatory protein HetR and the global nitrogen regulator NtcA during heterocyst development Alicia Ana Valladares Enrique Flores Antonia Herrero doi:10.1046/j.1365-2958.2002.02970.x Molecular Microbiology, Vol. 44, No. 5. (2002), pp. 1377-1385. 2008-05-09T14:33:23-00:00 2002 Molecular Microbiology 44 5 1377 1385 biochempaper cyanobacteria hetr ntca http://www.citeulike.org/user/cbg/article/2775324 <i>Proceedings of the National Academy of Sciences, Vol. 101, No. 14. (6 April 2004), pp. 4848-4853.</i><br /><br />HetR plays a key role in regulation of heterocyst differentiation. When the Cys-48 residue of the HetR from Anabaena sp. PCC 7120 was replaced with an Ala residue, the mutant HetR (HetRC48A) could not dimerize, indicating that HetR forms a homodimer through a disulfide bond. The Anabaena strain C48, containing the hetRc48a gene, could not produce HetR homodimer and failed to form heterocyst. We show that HetR is a DNA-binding protein and that its homodimerization is required for the DNA binding. HetR binds the promoter regions of hetR, hepA, and patS, suggesting a direct control of the expression of these genes by HetR. We present evidence that shows that the up-regulation of patS and hetR depends on DNA binding by HetR dimer. The pentapeptide RGSGR, which is present at the C terminus of PatS and blocks heterocyst formation, inhibits the DNA binding of HetR and prevents hetR up-regulation. 10.1073/pnas.0400429101 HetR homodimer is a DNA-binding protein required for heterocyst differentiation, and the DNA-binding activity is inhibited by PatS Xu Huang Yuqing Dong Jindong Zhao doi:10.1073/pnas.0400429101 Proceedings of the National Academy of Sciences, Vol. 101, No. 14. (6 April 2004), pp. 4848-4853. 2008-05-09T11:37:24-00:00 2004 Proceedings of the National Academy of Sciences 101 14 4848 4853 biochempaper cyanobacteria hetr pats http://www.citeulike.org/user/cbg/article/2773843 <i>Science, Vol. 282, No. 5390. (30 October 1998), pp. 935-938.</i><br /><br />10.1126/science.282.5390.935 Heterocyst Pattern Formation Controlled by a Diffusible Peptide Ho-Sung Yoon James Golden doi:10.1126/science.282.5390.935 Science, Vol. 282, No. 5390. (30 October 1998), pp. 935-938. 2008-05-09T00:36:51-00:00 1998 Science 282 5390 935 938 biochempaper cyanobacteria heterocyst hetr http://www.citeulike.org/user/cbg/article/2773726 <i>Archives of Microbiology, Vol. 169, No. 5. (18 April 1998), pp. 417-426.</i><br /><br />Abstract   The hetR gene plays an important role in heterocyst development and pattern formation in heterocystous cyanobacteria. The hetR gene from Anabaena sp. PCC 7120 was overexpressed in Escherichia coli. Antibodies raised against the recombinant HetR protein (rHetR) were used to characterize metabolism of the HetR of Anabaena sp. PCC 7120 in vivo. HetR was present at a low level when Anabaena sp. PCC 7120 was grown in the presence of combined nitrogen. Shifting from nitrogen repletion conditions to nitrogen depletion conditions led to a two fold increase of HetR in total cell extracts, and most of HetR was located in heterocysts. The amount of HetR in total cellular extracts increased rapidly after shifting to nitrogen depletion conditions and reached a maximum level 3 h after the shift. Isoelectrofocusing electrophoresis revealed that the native HetR had a more acidic isoelectric point than did rHetR. After combined nitrogen was added to the nitrogen-depleted cultures, the degradation of HetR depended on culture conditions: before heterocysts were fully developed, HetR was rapidly degraded; after heterocysts were fully developed, HetR was degraded much more slowly. The distribution of HetR in other species of cyanobacteria was also studied. Characterization of HetR protein turnover in Anabaena sp. PCC 7120 Ruanbao Zhou Zongxun Cao J Zhao doi:10.1007/s002030050592 Archives of Microbiology, Vol. 169, No. 5. (18 April 1998), pp. 417-426. 2008-05-08T22:35:08-00:00 1998 Archives of Microbiology 169 5 417 426 biochempaper cyanobacteria heterocyst hetr http://www.citeulike.org/user/cbg/article/2773622 <i>Journal of bacteriology, Vol. 182, No. 6. (March 2000), pp. 1575-1579.</i><br /><br />HetR is a serine-type protease required for heterocyst differentiation in heterocystous cyanobacteria under conditions of nitrogen deprivation. We have identified the active Ser residue of HetR from Anabaena sp. strain PCC 7120 by site-specific mutagenesis. By changing the S152 residue to an Ala residue, the mutant protein cannot be labeled by Dansyl fluoride, a specific serine-type protein inhibitor. The mutant protein showed no autodegradation in vitro. The mutant hetR gene was introduced into Anabaena strain 884a, a hetR mutant. The resultant strain, Anabaena strain S152A, could not form heterocysts under conditions of nitrogen deprivation even though the up-regulation of the mutant hetR gene was induced upon removal of combined nitrogen. The Anabaena strain 216, which carries a mutant hetR gene encoding S179N HetR and could not form heterocysts, also produced HetR protein upon induction. Sequence comparison shows that Ser152 is conserved in all cyanobacterial HetR. Immunoblotting was used to study HetR induction in both the wild-type and mutant strains. The amount of mutant HetR in strain S152A and in strain 216 increased continuously for 24 h after nitrogen step-down, while the amount of HetR in wild-type cells reached a maximum level within 6 h after nitrogen step-down. Our results show the Ser152 is the active site of HetR. The protease activity is required for heterocyst differentiation and might be needed for repression of HetR overproduction under conditions of nitrogen deprivation. Identification of the active site of HetR protease and its requirement for heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120. Y Dong X Huang XY Wu J Zhao Journal of bacteriology, Vol. 182, No. 6. (March 2000), pp. 1575-1579. 2008-05-08T21:38:25-00:00 2000 Journal of bacteriology 0021-9193 182 6 1575 1579 biochempaper cyanobacteria heterocyst hetr http://www.citeulike.org/user/cbg/article/2773446 <i>Molecular Microbiology, Vol. 9, No. 1. (1993), pp. 77-84.</i><br /><br />Summary The spatially patterned differentiation of hetero-cysts in the filamentous cyanobacterium Anabaena requires a functional hetR gene. Transcriptional fusions to luxAB show that hetR is transcribed at a low level throughout the filament when Anabaena is grown with combined nitrogen, and that induction of the gene begins within 2 h following nitrogen deprivation. By 3.5 h, induction is localized to spaced foci. By 6h, there is an overall induction of at least threefold in whole cultures, reflecting at least a 20-fold increase within spatially separated cells. The induction requires the presence of a functional hetR gene, indicating that hetR is autoregulatory. Full induction of a heterocyst structural gene, hepA, also requires a functional hetR locus. Spatial expression and autoregulation of hetR, a gene involved in the control of heterocyst development in Anabaena Todd Black Yuping Cai Peter Wolk doi:10.1111/j.1365-2958.1993.tb01670.x Molecular Microbiology, Vol. 9, No. 1. (1993), pp. 77-84. 2008-05-08T19:34:10-00:00 1993 Molecular Microbiology 9 1 77 84 biochempaper heterocyst hetr http://www.citeulike.org/user/cbg/article/2773413 <i>Proceedings of the National Academy of Sciences, Vol. 95, No. 9. (28 April 1998), pp. 4959-4963.</i><br /><br />10.1073/pnas.95.9.4959 Evidence that HetR protein is an unusual serine-type protease Ruanbao Zhou Xingcheng Wei Nan Jiang Huiguang Li Yuqing Dong Kuo-L Hsi Jindong Zhao doi:10.1073/pnas.95.9.4959 Proceedings of the National Academy of Sciences, Vol. 95, No. 9. (28 April 1998), pp. 4959-4963. 2008-05-08T19:08:15-00:00 1998 Proceedings of the National Academy of Sciences 95 9 4959 4963 biochempaper heterocyst hetr http://www.citeulike.org/user/cbg/article/2771941 <i>Science, Vol. 282, No. 5390. (30 October 1998), pp. 891-892.</i><br /><br />10.1126/science.282.5390.891 DEVELOPMENT:How Cyanobacteria Count to 10 Robert Haselkorn doi:10.1126/science.282.5390.891 Science, Vol. 282, No. 5390. (30 October 1998), pp. 891-892. 2008-05-08T14:50:39-00:00 1998 Science 282 5390 891 892 biochempaper heterocyst hetr