A new calmodulin binding motif for inositol 1,4,5-trisphosphate 3-kinase regulation

Inositol 1,4,5-triphoshate 3-kinase (IP3 3-K) is a key enzyme that catalyses the synthesis of inositol 1,3,4,5-tetrakisphosphate (IP4), using IP3 and ATP as substrates. Both inositides, substrate and product, present crucial roles in the cell. IP3 is a key point in Ca2+ metabolism that promotes Ca2+ release from intracellular stores and together with IP4 regulates Ca2+ homeostasis. In addition, IP4 is involved in the immune cell development. It has been proved that Ca2+/calmodulin (Ca2+/CaM) regulates the activity of IP3 3-K, via direct interaction between both enzymes. Although we have extensive structural knowledge of the kinase domains of the three IP3 3-K isoforms, no structural information is available about the interaction between IP3 3-K and Ca2+/CaM. Here we describe the crystal structure of the complex between human Ca2+/CaM and the CaM binding region of human IP3 3-K isoform A (residues 158 to 183), and propose a model for a complex including the kinase domain. The structure obtained allowed us to identify all the key residues involved in the interaction, which have been evaluated by site directed mutagenesis, pull-down and fluorescence anisotropy experiments. The results allowed the identification of a new CaM binding motif expanding our knowledge about how CaM interacts with its partners.

Source: BJ Signal - August 7, 2014 Category: Biochemistry Authors: E Franco-Echevarria, J Ignacio Baños-Sanz, B Monterroso, A Round, J Sanz-Aparicio, B Gonzalez Tags: BJ Biomolecules Source Type: research