4O4C

Crystal Structure of an Inositol hexakisphosphate kinase apo-EhIP6KA

Summary for 4O4C

• Entry DOI: 10.2210/pdb4o4c/pdb
• Related: 4O4B 4O4D 4O4E 4O4F
• Descriptor: Inositol hexakisphosphate kinase (2 entities in total)
• Functional Keywords: pdkg kinase, inositol phosphate, transferase
• Biological source: Entamoeba histolytica
• Total number of polymer chains: 2
• Total formula weight: 59798.39

Authors

Wang, H.,Shears, S.B. (deposition date: 2013-12-18, release date: 2014-06-18, Last modification date: 2023-09-20)

Primary citation

Wang, H.,DeRose, E.F.,London, R.E.,Shears, S.B.
IP6K structure and the molecular determinants of catalytic specificity in an inositol phosphate kinase family.
Nat Commun, 5:4178-4178, 2014

PubMed Abstract: Inositol trisphosphate kinases (IP3Ks) and inositol hexakisphosphate kinases (IP6Ks) each regulate specialized signalling activities by phosphorylating either InsP3 or InsP6 respectively. The molecular basis for these different kinase activities can be illuminated by a structural description of IP6K. Here we describe the crystal structure of an Entamoeba histolytica hybrid IP6K/IP3K, an enzymatic parallel to a 'living fossil'. Through molecular modelling and mutagenesis, we extrapolated our findings to human IP6K2, which retains vestigial IP3K activity. Two structural elements, an α-helical pair and a rare, two-turn 310 helix, together forge a substrate-binding pocket with an open clamshell geometry. InsP6 forms substantial contacts with both structural elements. Relative to InsP6, enzyme-bound InsP3 rotates 55° closer to the α-helices, which provide most of the protein's interactions with InsP3. These data reveal the molecular determinants of IP6K activity, and suggest an unusual evolutionary trajectory for a primordial kinase that could have favored efficient bifunctionality, before propagation of separate IP3Ks and IP6Ks.

PubMed: 24956979
DOI: 10.1038/ncomms5178

Experimental method

X-RAY DIFFRACTION (2.2 Å)