NtcA transcriptional factor: A global nitrogen regulator and connecting link between nitrogen metabolism and other crucial metabolisms

Abstract

Nitrogen fixing cyanobacteria play a crucial role in extracting and supplying biologically useful nitrogen to the biosphere. Nitrogen is the essential building block for the synthesis of proteins and amino acids. Nitrogen deficiency leads to several unavoidable consequences. In cyanobacteria, heterocyst is the site for nitrogen fixation under nitrogen starved condition. Heterocyst provides microoxic environment required for the nitrogenase enzyme activity. Nitrogen fixation is the highly regulated phenomenon in cyanobacteria. NtcA is the transcriptional factor regulating wide range of genes involved in the nitrogen metabolism. NtcA is a protein dimer which binds to the upstream promoter region of target genes (such as those involved in heterocyst differentiation and nitrogen fixation) at a specific site known as NtcA box having consensus sequence “GTAN8TAC.” NtcA act both as activator and repressor of variety of genes in cyanobacteria. Apart from regulating nitrogen fixation, NtcA also coordinates genes involved several other metabolisms such as photosynthesis, iron metabolism, oxidative stress etc., hence considered as a global transcriptional regulator. Considering the utmost importance of this particular protein for cyanobacteria, this article is devoted to discuss about the ntcA, its expression and the mechanisms of its regulation. Further, NtcA dependent regulations of different metabolisms are also discussed to understand the connections between nitrogen metabolism and other crucial metabolisms. © 2017 by Nova Science Publishers, Inc. All rights reserved.