Amino acid sequences calmodulin-dependent kinases

Fig. 8. Amino acid sequences of the model calmodulin-binding peptide, CBPS, and of the proposed calmodulin-binding domains of four calmodulin-dependent kinases. The + symbols on the bottom row indicate positions where a positively charged residue occurs in at least half of the aligned sequences, the Hb symbol refers to positions generally occupied by hydrophobic residues.

Phosphorylase kinase activity has an absolute requirement for Ca +, which binds to the 5-subunit. The amino acid sequence of this subunit is nearly identical to that of calmodulin, with four calcium binding sites, but unlike calmodulin, the 5-subunit is an integral part of the enzyme and does not dissociate from it in the absence of Ca +. In the presence of Ca +, kinase activity is further increased by phosphorylation of the a- and j6-subunits, catalyzed by cAMP-dependent protein kinase and several other kinases. Phosphorylation may activate the enzyme by disinhibiting... 

Several examples of proteins involved in signal transduction pathways are reported to be encoded by auxin-induced mRNAs. These include the 3-subunit of a heterotrimeric G-protein (arcA) [105,106], cyclin-dependent protein kinases (cdc2s) [107-111], and calmodulin (PCM-1 and arCAM) [112,113]. Putative transcription factors are also represented in the list of auxin-induced mRNAs. Auxin-responsive cDNA clones for a G-box binding bZIP transcription factor (SGBF-1) [114] and a homeobox transcription factor (Athb-8) have been reported [115]. Another auxin-responsive mRNA, dbp, was proposed to be a lysine-rich nuclear protein similar to HI histone, and the recombinant protein was shown to bind nonspecilically to DNA [116]. The amino acid sequence of dbp is, however, highly similar (i.e., 67% identity and 80% similarity) to a potato plasma membrane-associated protein called remorin [117]. The remorin protein binds to both simple and complex galacturonides as well as DNA, but is not a nuclear protein in potato... 

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