Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in Anabaena sp. PCC 7120

Yunming Shi, Weixing Zhao, Wei Zhang, Zi Ye, Jindong Zhao

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Calcium ions are important to some prokaryotic cellular processes, such as heterocyst differentiation of cyanobacteria. Intracellular free Ca 2+concentration, [Ca2+]i, increases several fold in heterocysts and is regulated by CcbP, a Ca2+-binding protein found in heterocyst-forming cyanobacteria. We demonstrate here that CcbP is degraded by HetR, a serine-type protease that controls heterocyst differentiation. The degradation depends on Ca2+ and appears to be specific because HetR did not digest other tested proteins. CcbP was found to bind two Ca2+ per molecule with KD values of 200 nM and 12.8 μM. Degradation of CcbP releases bound Ca2+ that contributes significantly to the increase of [Ca2+]i during the process of heterocyst differentiation in Anabaena sp. strain PCC 7120. We suggest that degradation of CcbP is a mechanism of positive autoregulation of HetR. The down-regulation of ccbP in differentiating cells and mature heterocysts, which also is critical to the regulation of [Ca2+] i, depends on NtcA. Coexpression of ntcA and a ccbP promoter-controlled gfp in Escherichia coli diminished production of GFP, and the decrease is enhanced by α-ketoglutarate. It was also found that NtcA could bind a fragment of the ccbP promoter containing an NtcA-binding sequence in a α-ketoglutarate-dependent fashion. Therefore, [Ca2+] i is regulated by a collaboration of HetR and NtcA in heterocyst differentiation in Anabaena sp. strain PCC 7120.

Original languageEnglish (US)
Pages (from-to)11334-11339
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number30
DOIs
StatePublished - Jul 25 2006

Keywords

  • Cyanobacteria
  • Protease

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in Anabaena sp. PCC 7120'. Together they form a unique fingerprint.

Cite this