Heme-regulated eukaryotic initiation factor 2a (eIF2a) kinase (HRI),
functions in response to heme shortage in reticulocytes and aids in the
maintenance of a heme:globin ratio of 1:1. Under normal conditions, heme
binds to HRI and blocks its function.
Chimeric calcium/calmodulin dependent protein kinase
(CCaMK) is characterized by the presence of a visinin-like
-binding domain unlike other known calmodulin-dependent kinases. Ca
-Binding to the visinin-like domain
leads to autophosphorylation and changes in the affinity
for calmodulin [Sathyanarayanan P.V., Cremo C.R. &
Poovaiah B.W. (2000)J. Biol. Chem. 275, 30417–30422].
Here, we report that the Ca
-stimulated autophosphory-lation of CCaMK results in time-dependent loss of enzyme
DYRK1A is a dual-specificity protein kinase that autophosphorylates a
conserved tyrosine residue in the activation loop but phosphorylates exoge-nous substrates only at serine or threonine residues. Tyrosine autophospho-rylation of DYRKs is a one-off event that takes place during translation
and induces the activation of the kinase.
2-Cys peroxiredoxins (2-Cys Prx) are ubiquitous thiol-containing peroxidas-es that have been implicated in antioxidant defense and signal transduction.
Although their biochemical features have been extensively studied, little is
known about the mechanisms that link the redox activity and non-redox
The highly conserved, atypical RIO serine protein kinases are found in all
organisms, from archaea to man. In yeast, the kinase activity of Rio2 is
necessary for the final processing step of maturing the 18S ribosomal
rRNA. We have previously shown that the Rio2 protein from Archaeo-globus fulgidus contains both a small kinase domain and an N-terminal
winged helix domain.
Cryptochromes are blue-light photoreceptors sharing
sequence similarity to photolyases, a class of flavoenzymes
catalyzing repair ofUV-damagedDNAvia electron transfer
mechanisms. Despite significant amino acid sequence simi-larity in both catalytic and cofactor-binding domains,
cryptochromes lack DNA repair functions associated with
photolyases, and the molecular mechanism involved in
cryptochrome signaling remains obscure.