Biology Reference
In-Depth Information
4.14.8
NO Synthase as CaM-Binding Protein
In Arabidopsis , a NO synthase (NOS) protein contains CaM-binding motifs and full
activation of the enzyme needs both Ca 2+ and CaM (Guo et al. 2003 ; Zeidler et al.
2004 ). NO synthesis is tightly regulated by a signaling cascade involving Ca 2+ infl ux
in elicitor-treated tobacco cells (Lamotte et al. 2004 ). NOS is involved in NO pro-
duction, which is stimulated by CaM and changes in [Ca 2+ ]cyt (Guo et al. 2003 ).
4.14.9
MAPK Phosphatase as a CaM-Binding Protein
Mitogen-activated protein kinase (MAPK) cascade is an important signaling
cascade involved in defense response (Mészáros et al. 2006 ; D
czi et al. 2007 ; Hall
et al. 2007 ). The activity of MAPKs is strictly regulated via phosphorylation of the
conserved T X Y motif, which is accomplished by a corresponding MAPK kinase.
After activation, the dephosphorylation and inactivation of MAPK is performed by
MAPK phosphatases (Theodosiou and Ashworth 2002 ; Yamakawa et al. 2003 ;
Katou et al. 2005 ). A putative MAPK phosphatase in Nicotiana tabacum (NtMKP1)
has been identifi ed as a CaM-binding protein (Yamakawa et al. 2003 ). In the pres-
ence of free Ca 2+ , NtMKP1 binds to CaMs. The CaM-binding domain was identifi ed
as a 52-amino acid sequence between the conserved gelsolin and Serrich domain in
the middle of the NtMKP1 protein (Rainaldi et al. 2007 ). A rice MAPK phospha-
tase, OsMKP1, has been shown to bind calmodulin (Katou et al. 2007 ). These
results suggest an interaction between Ca 2+ -CaM and a component of the MAPK
signaling cascade in plants.
ό
4.14.10
Calmodulin Binding Transcription Activators
(CAMTAs)
One family of CaM-binding proteins, designated as the calmodulin-binding tran-
scription activator (CAMTA) family resembles a group of putative transcription
activators identifi ed in the human genome (Bouché et al. 2002 ; Galon et al. 2010a ,
b ). The C-terminal CaM binding domain of CAMTAs mediates interactions with
calmodulin (Kudla et al. 2010 ). The CAMTA family of proteins contains a tran-
scription activation domain and two types of DNA-binding domains designated
the CG1 domain and the transcription factor immunoglobulin domain, ankyrin
repeats, and a varying number of IQ CaM-binding motifs (Bouché et al. 2002 ).
Arabidopsis thaliana contains six CAMTA genes ( AtCAMTA1 - AtCAMTA6 ).
CAMTAs comprise a conserved family of transcription factors (Bouché et al.
2002 ). AtCAMTA homologue is found in rapeseed (BnCAMTA) (Zegzouti et al.
1999 ; Bouché et al. 2002 ).
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