1.2. PAS Kinase StructurePAS selleck kinase inhibitor kinase is broadly evolutionarily conserved amongst eukaryotes, having homologs in yeast, drosophila, mice and man, but is not found in C. elegans. Its sequence contains a C-terminal serine-threonine kinase domain and an N-terminal Inhibitors,Modulators,Libraries Per-ARNT-Sim (PAS) domain. By primary amino acid sequence, the serine-threonine kinase domain lies near the CAMK branch on the human kinome dendrogram [17]. The N-terminal PAS domain belongs to a large superfamily of PAS domains, comprising over 21,000 PFAM entries from all kingdoms of life [18,19]. PAS domains are sensory domains that frequently regulate an attached functional domain in cis, often by serving as a protein interaction surface. PAS domains are found attached to a variety of functional domains, including transcriptional activators, guanylate cyclases, phosphodiesterases, ion channels and kinases.
Some PAS domains bind ligands within their cores allowing them to sense a variety of transient cellular and environmental conditions. PAS domains can either bind ligands reversibly like Inhibitors,Modulators,Libraries the citrate sensor CitA [20], or constitutively like the covalent binding of 4-hydroxycinnamic Inhibitors,Modulators,Libraries acid by the blue Inhibitors,Modulators,Libraries light sensing photoactive yellow protein [21,22] or the non-covalent heme-binding oxygen-sensing protein FixL [23]. PAS domains display low sequence conservation and high functional diversity, yet they contain a structurally conserved core of a five-stranded anti-parallel beta sheet surrounded by several alpha helices [19].
The conservation of general structure combined with the malleability of function make PAS domains good targets for structure-based design of artificial sensors where sensory PAS domains are covalently linked to effector domains of choice [24�C26]. For example, M?glich et al. recently replaced the oxygen-sensing Brefeldin_A PAS domain of Bradyrhizobium japonicum FixL with the LOV photosensory PAS domain of Bacillus subtilis, resulting in a chimeric kinase that was regulated by blue light instead of oxygen [24]. In addition, a plant derived blue-light sensing PAS domain has been fused to dihydrofolate reductase (DHFR) from E. coli, a protein that is not normally regulated by PAS domains. Remarkably, this fusion protein exhibited DHFR activity that was modestly regulated by blue light even without optimization of the construct [25].A high resolution NMR structure of the human PAS kinase (hPASK) PAS domain was solved in the lab of Dr.
Kevin Gardner [27] and it was found to be similar to other PAS domains including the well-characterized FixL heme-based oxygen sensor of Rhizobia [27]. The hPASK PAS domain www.selleckchem.com/products/CAL-101.html adopts the typical ��/�� PAS domain fold with several �� helices (C��, D��, E�� and F��) surrounded by a 5-stranded (A��, B��, G��, H��, and I��) antiparallel beta sheet. In addition, the PAS domain contains an unusually long and dynamic loop segment (F��/FG loop).