TY - JOUR
T1 - Regulation of intracellular free calcium concentration during heterocyst differentiation by HetR and NtcA in Anabaena sp. PCC 7120
AU - Shi, Yunming
AU - Zhao, Weixing
AU - Zhang, Wei
AU - Ye, Zi
AU - Zhao, Jindong
PY - 2006/7/25
Y1 - 2006/7/25
N2 - 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.
AB - 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.
KW - Cyanobacteria
KW - Protease
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U2 - 10.1073/pnas.0602839103
DO - 10.1073/pnas.0602839103
M3 - Article
C2 - 16849429
AN - SCOPUS:33746583497
SN - 0027-8424
VL - 103
SP - 11334
EP - 11339
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 30
ER -