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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