crystal-structure-n-terminal-domain-ryanodine-receptor-from-plutella

Crystal Structure of the N-terminal Domain of Ryanodine Receptor from <em>Plutella xylostella</em>

Development of potent and efficient insecticides targeting insect ryanodine receptors (RyRs) has been of great interest in the area of agricultural pest ...

Tianjin University

Fujian Agriculture and Forestry University

Ryanodine receptors (RyRs) are large calcium-release channels located in sarcoplasmic reticulum membrane. They play a central role in excitation-contraction coupling of muscle cells. Three commercialized insecticides targeting pest RyRs generate worldwide sales over 2 billion U.S. dollars annually, but the structure of insect RyRs remains elusive, hindering our understanding of the mode of action of RyR-targeting insecticides and the development of insecticide resistance in pests. Here we present the crystal structure of RyR N-terminal domain (NTD) (residue 1-205) at 2.84 Å resolution from the diamondback moth (DBM), Plutella xylostella, a destructive pest devouring cruciferous crops all over the world. Similar to its mammalian homolog, DBM RyR NTD consists of a beta-trefoil folding motif and a flanking alpha helix. Interestingly, two regions in NTD interacting with neighboring domains showed distinguished conformations in DBM relative to mammalian RyRs. Using homology modeling and molecular dynamics simulation, we created a structural model of the N-terminal three domains, showing two unique binding pockets that could be targeted by potential species-specific insecticides. Thermal melt experiment showed that the stability of DBM RyR NTD was higher than mammalian RyRs, probably due to a stable intra-domain disulfide bond observed in the crystal structure. Previously DBM NTD was shown to be one of the two critical regions to interact with insecticide flubendiamide, but isothermal titration calorimetry experiments negated DBM NTD alone as a major binding site for flubendiamide.

Crystal structure of ryanodine receptor N-terminal domain from Plutella xylostella reveals two potential species-specific insecticide-targeting sites.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a condition that is characterized by an abnormal heart rhythm in response to physical or emotional stress. The majority CPVT patients carry mutations in the RYR2 gene that encodes the calcium release channel/ryanodine receptor (RyR2) in cardiomyocytes. The pathogenic mechanisms that account for the clinical phenotypes of CPVT are still elusive. We have identified a de novo mutation, A165D, from a CPVT patient. We found that CPVT phenotypes are recapitulated in A165D knock-in mice. The mutant RyR2 channels enhanced sarcoplasmic reticulum Ca release, triggered delayed afterdepolarization in cardiomyocytes. Structural analysis revealed that the A165D mutation is located in a loop that is involved in inter-subunit interactions in the RyR2 tetrameric structure, it disrupted conformational stability of the RyR2, which favored a closed-to-open state transition, resulting in a leaky channel. The loop also harbors several other CPVT mutations, which suggests a common pathogenic molecular mechanism of CPVT-causing mutations. Our data illustrated disease-relevant functional defects and provide a deeper mechanistic understanding of a life-threatening cardiac arrhythmia.

Pathogenic mechanism of a catecholaminergic polymorphic ventricular tachycardia causing-mutation in cardiac calcium release channel RyR2.

Calmodulin (CaM) is a Ca-binding protein that plays an important role in cellular Ca-signaling. CaM interacts with diverse downstream target proteins and regulates their functions in a Ca-dependent manner. CaM changes its conformation and hydrophobicity upon [Ca] change and consequently changes its interaction with CaM-binding domains from the targets. Based on these special properties of CaM, it was used as an affinity tag to develop a novel purification strategy by using it for two sequential orthogonal purification steps: 1) an affinity purification step, in which CaM-tag interacts with an immobilized CaM-binding domain; and 2) a hydrophobic interaction chromatography step, during which CaM binds to a phenyl sepharose column. In both steps, the CaM-tagged protein binds in the presence of Ca and unbinds in the presence of ethylenediaminetetraacetic acid (EDTA). An optional third step can be added to remove the CaM-tag if necessary. We used green fluorescent protein (GFP) as a test protein to demonstrate the effectiveness of the method. High yield and high purity of GFP with proper function was obtained using this novel strategy. We believe that this method can be applied to a wide range of protein targets for structural and functional studies.

A two-step purification strategy using calmodulin as an affinity tag.

Rose has been entwined with human culture and history. "Blue rose" in English signifies unattainable hope or an impossible mission as it does not exist naturally and is not breedable regardless of centuries of effort by gardeners. With the knowledge of genes and enzymes involved in flower pigmentation and modern genetic technologies, synthetic biologists have undertaken the challenge of producing blue rose by engineering the complicated vacuolar flavonoid pigmentation pathway and resulted in a mauve-colored rose. A completely different strategy presented in this study employs a dual expression plasmid containing bacterial idgS and sfp genes. The holo-IdgS, activated by Sfp from its apo-form, is a functional nonribosomal peptide synthetase that converts l-glutamine into the blue pigment indigoidine. Expression of these genes upon petal injection with agro-infiltration solution generates blue-hued rose flowers. We envision that implementing this proof-of-concept with obligatory modifications may have tremendous impact in floriculture to achieve a historic milestone in rose breeding.

Zhiguang Yuchi

Tianjin University

Crystal Structure of the N-terminal Domain of Ryanodine Receptor from Plutella xylostella