In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 30 ( 2006-07-25), p. 11334-11339
Kurzfassung:
Calcium ions are important to some prokaryotic cellular processes, such as heterocyst differentiation of cyanobacteria. Intracellular free Ca 2+ concentration, [Ca 2+ ] i , increases several fold in heterocysts and is regulated by CcbP, a Ca 2+ -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 Ca 2+ and appears to be specific because HetR did not digest other tested proteins. CcbP was found to bind two Ca 2+ per molecule with K D values of 200 nM and 12.8 μM. Degradation of CcbP releases bound Ca 2+ that contributes significantly to the increase of [Ca 2+ ] 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 [Ca 2+ ] 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, [Ca 2+ ] i is regulated by a collaboration of HetR and NtcA in heterocyst differentiation in Anabaena sp. strain PCC 7120.
Materialart:
Online-Ressource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0602839103
Sprache:
Englisch
Verlag:
Proceedings of the National Academy of Sciences
Publikationsdatum:
2006
ZDB Id:
209104-5
ZDB Id:
1461794-8
SSG:
11
SSG:
12
