title: Activation of SsoPK4, an Archaeal eIF2α Kinase Homolog, by Oxidized CoA.
abstract: The eukaryotic protein kinase (ePK) paradigm provides integral components for signal transduction cascades throughout nature.However, while so-called typical ePKs permeate theEucaryaandBacteria,atypical ePKs dominate the kinomes of theArchaea. Intriguingly, the catalytic domains of the handful of deduced typical ePKs from the archaeonSulfolobus solfataricusP2 exhibit significant resemblance to the protein kinases that phosphorylate translation initiation factor 2α (eIF2α) in response to cellular stresses. We cloned and expressed one of these archaeal eIF2α protein kinases, SsoPK4. SsoPK4 exhibited protein-serine/threonine kinase activity toward several proteins, including theS. solfataricushomolog of eIF2α, aIF2α. The activity of SsoPK4 was inhibitedin vitroby 3',5'-cyclic AMP (Kiof ~23 µM) and was activated by oxidized Coenzyme A, an indicator of oxidative stress in theArchaea.Activation enhanced the apparent affinity for protein substrates, Km, but had little effect on Vmax. Autophosphorylation activated SsoPK4 and rendered it insensitive to oxidized Coenzyme A.
authors.affiliation: Department of Biochemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA. wkray@vt.edu.
authors.forename: William K
authors.initials: WK
authors.lastname: Ray
authors.affiliation: Department of Biochemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA. mpotters@vt.edu.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Potters
authors.affiliation: Department of Chemistry, Centre College, Danville, KY 40422, USA. january.haile@centre.edu.
authors.forename: January D
authors.initials: JD
authors.lastname: Haile
authors.affiliation: Department of Biochemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA. pjkennel@vt.edu.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kennelly
keywords: crenarchaea; protein phosphorylation; stress signaling